It is essential to the American myth that North America was wilderness when the European colonists began to arrive. Sure, there were people, but they weren’t ‘civilized’ and therefore didn’t count; they could be brushed aside.
Charles C. Mann’s 1491 [amazon] and its sequel 1493 [amazon] oppose that myth. He can only hint at the complexity of the politics of the era but it’s overwhelming. Of course it is, it’s people doing the things people do.