I don't believe that inside Nazi Germany nor in Stalinist Russia, there was the problem of a foreign empire clashing with an indigenous culture.
It seems the best American analogue to the experiences of those regimes was what was done to Japanese Americans in WW2 - which while awful, thankfully, doesn't hold a candle to what was done to the German Jews or the Soviet victims of Stalinism.
The history of the world is filled with violent tribal conflict, usually over the right to settle and tax a given piece of land.
The Jews and Nazis weren't fighting for control over Bavaria.
The Europeans did not set out with the goal of exterminating the native Americans. The NAs had their land taken from them by force, which is how it has always worked on this planet.
There are two general possibilities for how to proceed from here
1) convince people that taking land from other people is immoral
2) find additional land that is both unsettled and desirable
#1 is worth working on, and can show some real improvements, but will ultimately not be enough.
#2 is also worth working on, and why I am a space nutter, and why I am interested in how seasteading plays out.
A mix of #1 and #2 may help humanity not kill each other completely. We've gone almost 70 years with the ability to wipe ourselves out and we haven't done so yet. That's an encouraging indicator.