People are going to approach this with different levels of mastery of the subject, with different assumptions, and they are naturally going to overlook things other people might see.
I'll suspend disbelief at various levels for various purposes. I enjoy Far Side cartoons in which cave-men co-exist with stegosaurus (and the Thagomizer). I've played D&D characters who could *reliably* expect that after falling fifty feet, they'd be able to stand up and fight (and/or sprint). I am not clear on the appropriate level of internal consistency for this thread, which starts with imagery from a dream.
There's a difference between asking from ignorance - "what do you think would happen? or "here's an idea, is it plausible?" - versus bold declarations made without fact-checking.
For example, the assertion that Custer's soldiers used muzzle-loading weapons. Would you say such a thing, without checking that it was true?
Who cares? Well, the idea that Indians (aka Native Americans, aka First Peoples, aka Trans-Bering Americans) were "savage" and "primitive" has been used to justify... you can call it conquest, or you can call it genocide, or Manifest Destiny, as you please. So people with differing agendas, on that topic, tell different stories of how the Lakota won at Little Bighorn. So it's related to touchy topics.
The assertion that "Indians" (aka Native Americans, aka First Peoples) didn't have the organization to build pyramids, can also fall on touchy ground. Does "Indian" include all the Trans-Bering peoples, including the Maya, Olmec, Nahuatl and Aztecs, and thus the builders of the Pyramid of the Sun at Tenochtitlan? Or does it only mean those who lived (and some who still live) in what's now Canada and the USA? Thomas Bowman's "the typical image of an American Indian was one of a warrior with face paint, buffalo hide clothing, moccasins, and a feathered head dress" sounds more Lakota than Aztec. (Also more Lakota than Hopi, Ohlone, Inuit, Algonquin or Chinook, unless any of those had access to buffalo hide.)
So I held off on the question of history, and simply gave my answer to the question of whether this could be a TRPG that I'd want to play. (And sparked a reference to the Sea Peoples - which is effectively an in-joke, among those of us familiar with the history of Egypt around 1250 BCE.) I'm kinda biting my tongue, on some other points.