2. If you're referring to Taiwan, it's only been 66 years, and Taiwan is relatively minor piece of China. Unless you're referring to India?
China spent the 19th century in intermittent civil wars during which warlords de facto ruled large swathes of the country. This century included the bloodiest conflict in human history, the Taiping rebellion. China spent the first 50 years of the 20th century in civil wars where warlords openly ruled most of the county and the president of China was fucking kidnapped that is an actual thing that happened.
I'm pretty sure that China didn't spend most of the preceeding 2 millenia unified either but I dont know my pre Qing history too well. It's mostly that the Communist Party has been pushing the "One Land" narrative singlemindedly for the past 60 years and those who pay attention to China tend to credulously believe what the exotic foreigners say about their "ancient" "nation".
It went through periods of mass fragmentation, but on the whole there was a single recognized "Imperial" government for the most part since 221BC. I'd have to disagree with the idea that during the rebellions (of which there have been MANY over the last two thousand years), China doesn't qualify as a unified state. The Taiping Rebellion lasted 14 years and at its fullest extent controlled about three provinces in total. And that was the largest rebellion in Chinese (or world) history. The bulk of China was still under Imperial control, and the areas under Taiping control were quickly reintegrated into the Imperial system after the rebellion. There wasn't time for governmental and cultural differences to take root.
Now, the warlord era of the 1930's...yeah, that's legit disunity more akin to the Ten Kingdoms and Five Dynasties period, where there really wasn't anybody in charge.
In India by contrast, it wasn't that there was a single Grand Maharajah and lots of rebellious states, it was lots of states with no overall hegemon. For a very long time, in between the periods where an outsider would come in and conquer most or all of the place (Mughals, British). And even then, they tended to leave the local rajas in control of their fiefdoms, so those regional differences had a long time to take root.
But hey, what do I know, I'm just one of those people who pay attention to China, ergo I'm swallowing that Commie propaganda, right?
China is 98% ethnic Han
I fail to believe this. Unless there are simple "language=ethnicity" kind of cheating.
Actually, you're correct. It's down to about 92% now days. And it comes partly from having a relatively broad definition of "Han" (and from a purely biological standpoint, northern Chinese are going to be different in ancestry from southern Chinese) and partly from just demographics -- the central and coastal plains support a population orders of magnitude larger than the peripheries, which is where most of the recognized ethnic minorities reside.
Linguistically, China is much more diverse, with just the Han population speaking 80+ different dialects.