Later in life, I found out why. It's not that I didn't like history, I just don't like the sanitized version taught to me in primary/secondary school. It's like corporate public relations where they vaguely acknowledge wrongdoing, but communicate in a very weaselly way to downplay it.
The rote response I hear from the USA fandom is always some variation of "WELL THEM INDIANS DID BAD THINGS TOO" and it's like... ok? Then why obfuscate? If everyone is equally bad or whatever weird thing you're trying to say, why not just lay out all the cards and let me decide for myself how to interpret the history?
For example, most of what is known about the Commanches comes from letters and diaries of white people who were in contact with them, or were enslaved by them.
See "Empire of the Summer Moon" by Gwynne.
https://www.amazon.com/Empire-Summer-Moon-Comanches-Powerful...
It's a fantastic account, and I'm amazed nobody has made an epic miniseries about it.
On an unrelated note, Gwynne's book is fine as a fantasy story, but it's very badly regarded from the perspective of narrative history. Hämäläinen's Comanche Empire is a much better book arguing a largely similar position. Don't take that as applying to later books by the same author, sadly.
As evidence of the paucity of historical knowledge of the Indian peoples, estimates of the pre-Columbian population vary from 10 million to 100 million.
I know about the various rock paintings with symbols, but there isn't enough of that to represent much of anything.