30,000 years worth of missing genetic immunity to essentially every disease imaginable wiped out native populations in the Americas and precipitated the collapse of civilizations there, actually.
That's irrelevant. The point of the story, if you missed it, is that Europeans were not interested in adopting the Native American way of life and assimilating.
Cortez didn't arrive in Mexico and swear loyalty to the local king, and adopt their religion
Another point of the story is that new populations are either going to assimilate (which could be great for the pre-existing population) or they aren’t going to assimilate (which could be pretty bad for the pre-existing population).
Cortes’s expedition of literal conquerors arrived by fighting for their lives the moment they met a state, let alone an empire.
Europe and its institutions failing to incorporate wildly conservative religious citizens has a lot more historicity than attributing “immigration” to the implication of native tribes in a post-apocalyptic pre-USA (it’s never Mexico or Peru) being culturally, physically, and biologically colonized.
Because wildly conservative religious people tend to abuse their religion to push their personal agenda. Hell you could say some candidates are pondering to them BECAUSE they know they are easily manipulated without upholding the core of their religion.