Teddy Roosevelt, in The Winning of the West, presented the American mentality a hundred years after the Revolution.
“No treaties, whether between civilized nations or not, can ever be regarded as binding in perpetuity. With changing conditions, circumstances may arise which render it not only expedient, but imperative and honorable, to abrogate them. Whether the whites won the land by treaty, by armed conquest, or, as was actually the case, by a mixture of both, mattered comparatively little so long as the land was won. It was all-important that it should be won for the benefit of civilization and in the interests of mankind. It is, indeed, a warped perverse, and silly morality which would forbid a course of conquest that has turned whole continents into the seats of mighty and flourishing civilized nations.” (p. 19)
“…the hard, energetic, practical men who do the rough pioneer work of civilization in barbarous lands are not prone to false sentimentality. The people who are, are the people who stay at home. Often these stay-at-homes are too selfish and indolent, too lacking in imagination, to understand the racial importance of the work which is done by their pioneer brethren in wild and distant lands. So they judge them by standards which would only be applicable to quarrels in their own townships and parishes.” (p. 20)
“The most ultimately righteous of all wars is a war with savages, though it is apt to be also the most terrible and inhuman. The rude, fierce settler who drives the savage from the land lays all civilized mankind under a debt to him.” (p. 21)
Berc0t: “The English policies guaranteed that the white man and the Indians would not be able to live in peace. Because they couldn’t live together, one side had to go. And that was the Indians. We’re talking about genocide….” (p. 22)
There is more I could have quoted from Teddy, but I hope his arrogance and disdain for the Native Americans (and those who might not join in the killing/colonizing) comes across clearly.