If we hadn't bombed Hiroshima or Nagasaki.
I wonder if the total war dead after Japan surrendered would equal the civilian casualties of the bomb.
That all depends on Japan's willingness to surrender. If they never actually did, or it took occupying the whole island, the casualties would have been dramatically higher. We'd also probably have a Communist North Japan and Capitalist South Japan.
If they surrendered once there was a significant show of force to demonstrate the seriousness of the invasion, or has some have (in my opinion, fallaciously) suggested, before there was any mainland invasion; the casualties would be less. Japan probably would not have surrendered to the USSR over the USA, but that's a What If in and of itself.
If I remember correctly, the Japanese government had sent several overtures of peace to the US through the USSR, but the US ignored those overtures for some reason or another (the USSR turning around and declaring war on Japan in a obvious bid to grab land certainly didn't help matters). So Japan was willing to surrender/make peace even before an invasion of the mainland. However I have no clue what the conditions of peace would be, or how the military hardliners would react in the event of a peace. I could easily see Japan becoming destabilized after the war depending on the terms of the peace treaty.
Well, the Soviets never passed along the overtures because they were already planning the invasion of Manchuria by that point; the Americans only learned about them because they had broken the Japanese diplomatic codes by that point. There's also the major issue of the Kyūjō and Matsue incidents, which took place after the destruction of Hiroshima and Nagasaki, and were respectively an attempted coup and uprising aimed at continuing the war. There was serious resistance to the idea of peace, even after the realization that the Americans could destroy every major Japanese stronghold, city, settlement, or large village without even the possibility of retaliation. As such, it is reasonable to suspect that any such offer of peace, even if it were genuine and not a facade intended to permit the Japanese time to rearm and rebuild, could not be followed through in good faith by the relatively-powerless Emperor in the face of opposition from the armed forces. Finally, there's also the issue that the Japanese flat-out refused to even consider unconditional surrender - they always demanded terms in return for peace. The fact that the Americans later offered similar terms was different, because at that point it was a demonstration of American power that they could offer, rather than conceding to Japanese power and negotiation. In other words, in the concept of "face", if America had accepted Japanese demands even in 1945, it would have been a demonstration of Japanese power that they could cling to in the post-war ere. Remember also that the example of Germany, which had seen its demands as a prerequisite for surrender accepted in 1918 and, with that as a suggestion of what power still remained to Germany even when the war was already lost to an objective observer, became the seed for the Dolchstosslegende, was still fresh in many people's minds in the wake of V-E Day so recently, and it is understandable to see why the willingness to accept unconditional surrender was considered a prerequisite for peace in both Germany and Japan. The fact that it was not required of Japan in the end was irrelevant, as long as Japan was forced to see the necessity of accepting it in order to confirm that they themselves saw it as a complete and total defeat of their cause and the malignant social structures that had created the war, rather than seeing themselves still in such a position of power that they could demand their own terms before surrendering their arms.
I always liked to imagine what would have happened if columbus had reached cuba, but had his entire expedition captured never to return to europe. the following scenario is that it could have taken another 200 years of other attempts at sailing west, again, only to be captured never to return. the repercussions of such events, could have introduced the wheel and the deep sea faring to the americans empires of the time and gave them enough time to recoup the losses that the european plagues brought upon them.
I think that even 200 years would have not been enough for the native americans to be able to come to the same level of technology europe had and eventually, some form of colonization would have due to happen anyway, but to a much lesser extent and with the native americans keeping their sit of powers at the larger empires. obviously, such an event, or, non event would have had an effect on the entire world, which is too complicated to predict. what would have happened with europe without the american gold and other resources? what were of the black africans, if there wasen't the same need of slaves? could europe gain its advantage over the ottomans?
Contrary to often popular belief, Columbus was neither the first, nor the only one to (attempt to) discover the New World. It might have delayed the eventual colonization by a few years, but it wouldn't be long before another idiot tried it, or even a Portugese trader blown out of course to stumble upon Brazilia.
That being said, the major problem for American civilizations was the extinction of the horse. This prevented fast, long range communication, and made forming , progressive civilizations significantly harder.
However, let us assume that the Americas were never colonized, or in fact never discovered. The Gold and Bullion crisis would have worsened, but I assume that Africa, and part of the Indies would take on the role of the Americas.
I can definitely confirm that it would have happened within the decade, no more - Cabral's expedition that discovered Brazil took place in 1500, and Colombus's first landing on the American mainland (as opposed to the scattered islands of the West Indies, Hispaniola, and Cuba) had only happened in 1498. Most of the Spanish exploration of the American mainland that led to the realization of the full magnitude of their discovery wasn't even reported back to Madrid by the time Cabral had left, and even if it had been, the Portuguese wouldn't have sent an entire Armada on an exploratory run any more than the Spanish had given Colombus an entire Armada to play with. Cabral's discovery of Brazil was just a consequence of Portuguese navigational methods, which called for a southwest run from Africa to catch the favorable winds that would bring them to the Cape of Good Hope (due to the South Atlantic gyre, which runs counterclockwise), and had always brought them very close to Brazil. Really, it's more surprising that the Portuguese hadn't discovered it sooner.
Also, a critical requirement for the colonization of Africa is, as MetalSlimeHunt points out, medical technology. One of the most critical of these is the mass production of a cure for malaria, which is what allowed for the establishment of mass trade and colonization of the African interior. Quinine was for quite some time the only such cure, was first identified and extracted from cinchona bark in a pure form in 1820, and only entered mass production in the mid-19th century. Just as a further catch, the only natural source of quinine is actually American in origin - the cinchona tree is native to Peru and Bolivia, and did not exist outside of the New World until the British and Dutch "obtained" samples of it from under the Spanish collective nose and began planting it in India and the DEI, respectively. Subsequent cures, such as chloroquine, didn't exist until the 20th century. In other words, a failure to discover the New World for 200 years would also completely disrupt imperialism in Africa and subtropical to tropical Asia, relegating European contact with these lands to trade.
Knock-on effects of a failure to establish a slave economy in the Americas hungry for labour would include, especially in sub-Saharan Africa, that the so-called "slaver empires" like Dahomey would never emerge without the money of the slave trade simultaneously fueling and giving motivation for their expansion and endless warfare. The collapse of overland Saharan trade and the resulting massive realignment of governments and power in Sub-Saharan Africa would still occur as it is replaced by naval trade around the coast in European hulls, with serious consequences for internal African trade, but without the trap of the slave trade (bleeding manpower and resources for gold), the economy of the region may reemerge among healthier, more stable lines than occurred historically. That is to say, they would become resource farms and economic satellites completely dependent on European trade for wealth, but of grains, ivory, mineral resources, and other trade goods that don't pertain to kidnapping people from other tribes and selling them to traders who will haul them across half the world. So, much like they are today, but that's still much better than states like Dahomey, Oyo, or the Zanj.
As for the Americans themselves, developing 200 years in isolation would not benefit them significantly at all. Simply put, they were effectively in the Stone Age compared to the Late Medieval/Early Modern Age of Europe, and they may possibly reach the Iron Age on their own, but pitting Hittites against redcoats is no better than Aztecs against conquistadors. They would have no motivation or impetus to advance at an accelerated rate, and the political institutions of both the Incas and Aztecs, the major political powers, were approaching a nadir (which played a large role in their historical defeats). However, they would likely remain in the same trap, and be even more hopelessly behind the Europeans of the 17th-18th centuries than they were behind the Europeans of the 15th-16th centuries.
As for settler nations that would still exist, primary ones would be Australia, New Zealand, and South Africa, which were among the few lands amenable to European settlement. British colonization, without the lessons learned in the New World from the rebellions in the 13 Colonies (successful) and both Canadas (unsuccessful) which culminated in the Durham Report and the concept of responsible government, would also be more likely to follow the model of most other European nations, highly authoritarian in nature, without as much in the way of self-determination. We may talk of an Australian Revolution in the 19th century instead of an American Revolution in the 18th century, for instance. Given how the British treated the Boers historically in that era (the Boer wars were prominent in the British "invention" of concentration camps) and how industrialization had changed the nature of warfare between the 18th and 19th centuries, it would likely not end well for the Australians. It is probable that the American settler nations would still develop over the 18th and 19th centuries, and given how badly the natives were treated historically, I am loathe to think of what industrialization of those methods would do. The 19th century is also one in which many weird and what we today consider offensive ideas of "race" developed, and to think of the treatment of these people in an industrialized manner with "scientific" backing is...not particularly pleasant. Australia, until the 1980s, used a very stark picture of race between the settler British and the aboriginals that was apparently systematized in law and resembles the American "one drop" view of blacks much more than the complex mulatto strains of the Code Noir and Spanish equivalents, understandably so given the two nations' common origins. Frontier violence, the systematic expulsion of natives from fertile lands or their subjugation in the name of the "white man's burden", all of this would still occur in a late-settled America, backed by the Maxim gun as a pithy poem of the era once noted. One positive consequence of a late colonization, though, would be the survival of local cultures to a greater degree than historical. Though the infancy of anthropology was one in which many of those aforementioned odd theories first emerged, it was also the first time in which the cultures of the conquered were regarded as subjects to be preserved for study instead of heathen targets to be destroyed in order to break their will.
Finally, I could also touch on Europe, which would see tremendous differences (the economic wealth extracted from the Spanish Main was absolutely critical in funding affairs like the 30 Years War, for instance), but I think I've made this into enough of a brick of a post, so I'll simply note one more thing. A failure to discover the New World entirely means we would never get chocolate or the gin and tonic. And isn't that worth destroying one or two or an uncounted myriad of potential civilizations?[/sarcasm]