You're skipping over the whole "manifest destiny" bit, where the remaining natives were systematically hunted down and destroyed. Trail of Tears ring any bells?
And note this was perpetrated by The United States, not the "American colonists". This was happening in the 1800s, a good 300 years after the initial disease front came through.
If the United States had respected the native populations the American West would look very different today. Compare with current Central and South America for example (which were certainly still victims of both disease and genocide, but it was less thorough due to differences in colonizers and geography).
And note this was perpetrated by The United States, not the "American colonists". This was happening in the 1800s, a good 300 years after the initial disease front came through.
If the United States had respected the native populations the American West would look very different today. Compare with current Central and South America for example (which were certainly still victims of both disease and genocide, but it was less thorough due to differences in colonizers and geography).