Your point about how there was that shift in native American peoples in the early 20th century is an important one to note. They become marginalized in that they aren’t the threat they were in the 19th century to expansion. The wars are over although the abuse continued. By the 1980’s there’s a huge shift.

That said, I think we tend to read the history in terms of the US too much. It’s interesting seeing quasi-fundamentalist use of the Book of Mormon prophesies in say southern Mexico and norther Guatemala in a fashion alien to most Mormons. (Who all too often neglect the warnings in 3 Nephi about the Lamanites to the Gentiles) To me the history of southern Mexico down a ways is much more interesting than what happens in the US. (Although obviously US history is tragic as well)

There’s a common way of reading the text that simply reads it as a history of the US. That itself is problematic if mesoAmerican settings fit the Book of Mormon best. But more importantly it means that the role of gentiles is being twisted somewhat by neglecting Mexico and Guatemala.