Dude you need to read up on how native Americans dealt with Europeans and Americans until they were forced on reservations, the black hills were a focal point of war and and while the Lakota Sioux are the current tribe most associated with them in the American cultural zeitgeist the Cheyenne and Arapaho have older links to those hills if I remember correctly. Hell going back to the sale of Manhattan was not the local tribe selling it but their enemy neighbor who sold the land and helped depopulate the island for the Dutch.

In short native American tribes had conflict and hatreds between themselves and fought eachother to their detriment until there was no other way to go forward than to unite.