So playing as Inca (started as the typical Cuzco) with MEIOU mod (but Ironman mode is still on), colonized almost the entire coastline of South America. Just a bit of the south of it is left uncolonized and Holland (never seen Holland colonize lol) took part of that south bit. And I can't declare war on him cause he is allies with England and England is my ally. Just waiting for when alliance breaks to move in.
My vassals: Chakas (or however its spelled) down in South America, Mayans and three Aztec (aztec hasn't formed, but you get the idea) nations (one is a tiny two province one though cause he broke away and then I pwned him). I wanted to leave the north natives alone for most part. So I'm pretty much leaving them alone the entire game, except to deal with petty wars and rebellions.
However, its a VERY tough game. Have had three wars with Spain, first one I did pretty good and would have done a lot better, but forgot to actually put a claim on his spanish Brazilian vassal. So the war ended with nothing for me lol. Since I entirely rely on ticking war score. Second war went a lot better, took all his south american territories and did really good defending against his troops (and his Sicily ally which was a pain in the ass to deal with). However, I pretty much prevented him from even thinking of colonizing South America. The only hard part of the 2nd war (and 1st which went even worse in this regard) was my fleet of ships just got slaughtered. I didn't have heavy ships at this time.
Third war, again against Spain. He had started colonizing North America, and he had a bunch of island provinces he was and had colonized. This war however went really badly, even though I accomplished what I wanted. For one, I probably should have made bigger use of my navy, but I was still building it up and didn't want to throw away ships. I was kinda nervous they'd get pwned again. I should have attacked the Sicily fleet with it though, AND had more troops along the coastal provinces. See, I had a huge army in Aztec land that I forgot about (30k or so troops) and they didn't need to be there anymore. I forgot I sent an army to deal with the rebellious vassal. I also had probably too big of an army around my capital, since they weren't doing anything.
However, Sicily landed ashore in the north part of South America. Which I also had to keep a better eye on where ships were along my coast, kinda focused on another part of the battle lol. And they went in and just slaughtered my smaller forces I had defending various places. They went all the way south, then went to attack my capital itself. Even with my troops defending, they would just get slaughtered by Sicily. Spanish never landed many troops for some reason, or he didn't do much with them. But wherever I went to defend, even with massive terrain bonuses (which I rely on a lot), it was no good. In the end, before the capital was taken, I managed to get a massive army to attack Sicily's invasion force and won (barely lol).
A whole bunch of factors went into getting pwned. For one, spain and sicily had a tech level of military higher than me, which gave them new troop types. I managed to get it after the war, but I bet that would have helped a LOT. I also didn't pay enough attention to where enemy fleets were, and I had a bunch of troops being useless in central America. And I should have made a bigger use of my fleet.
Luckily though cause I had the war goal that I put a claim on (that they never bothered to re-take, but did have a hefty force there), I managed to get all of Spain's colonies, AND all his island provinces (including two by Africa). And it was really useful (and probably helped the most) of having England be an ally. England even formed Canada lol, or his colonies did. But I don't see Spain colonizing the America's any time soon, as South America is pretty much secured along the coast from any colonization attempt. Except for Holland down south, but heh. Only place he could colonize is North America, but he doesn't have any provinces that are close to it now.
In the end, before I saved and got off. I took my two main forces and they are moving to one province along the coast, and then I'll split them up and put them in better locations so they can respond to any invasion landings better. I may end up putting castles along the coast as well, so it'll be a massive barrier (with provinces in between) of castles. I think that make it a lot easier to defend South America. But my income is shot (but I say that, and making nearly 90 gold a month lol. So many gold provinces
), so that is a long term plan and take a while to do. I can afford that no problem lol, its just building them takes up the money. I make so much gold