This is definitely an opinion question, which is something we generally don't do here, however, I will be happy to try and at least shed some light on this question.

There are a few reasons for this. First, is that in the modern context, most borders, as they exist today at least loosely resemble the borders throughout Europe at the close of the 18th century. Sure wars raged and chaos ensued, but even after the Napoleonic wars, two world wars, and countless others, most people were able to retain most, if not all, of their ancestral homeland. This is not the case with Native Americans. Worse is that European populations systematically destroyed and killed countless numbers of Native American populations, so much so, that only a tiny sliver of the numbers they once had lasted until the 20th century. In another question on Native American populations, I explained that it is estimated that in 1492, North America was expected to have between between 2-18 million people (Natives) living there. Most estimates that I've seen that the number is closer to 18, possibly as high as 25 million. This is significant, because by the time of the 1900 census (the first census that all Native Americans could take part in), there were less than 500,000 left. This is signifiant because populations should grow, not completely shrink up, and their shrinking is mostly due to mass warfare and forms of genocide.

The warfare against Native Americans was brutal and continuously required that the United States break countless treaties with them, and as a result, many died. This type of systematic warfare is not something we saw in Europe when enemies were fighting each other in war. It wasn't just about conquering and subjugating, but rather it was about decimating an enemy and not allowing their culture and people to survive.