I think what the author is saying is that the history taught in schools and colleges should not omit the part about the how the lands were acquired from the native americans.
It's interesting to me how we finally got rid of Original Sin, but now have replaced this with other, atheistic forms of this, like trying to make our children feel guilty about Native Americans and Slavery. I personally think this is the best way to increase tensions.
However, the US - like Russia, didn't colonize other "nations" it appears to have mostly completely supplanted them in the areas it grew into.
Of course, this is only of historical interest, but as a wise man once wrote: "Who controls the past controls the future".
And as far as more modern immigrants? Sorry, people knowingly chose to immigrate to a land which has been stolen. Again, there's a choice to do the right thing or not, and people are choosing to do the wrong thing. People should take responsibility, full stop.
The history and deeds of the native tribes of America have nothing, absolutely nothing to do with the current invading population. No non-native American has the moral right to even allude to it, let alone point fingers and try and force moral equivocations. It's the worst form of hypocrisy.
Time and time again people like to derail important discussions about the nature of Native American genocide and slavery by claiming this. Acknowledging this history is not about making people feel guilty, it is about understanding how those people are treated today and how their treatment is an extension of this history. The nature of racism and its history and legacy should not be trumped because it makes someone somewhere feel bad.
The best way to increase tensions is to ignore the past and continue to let that past influence how people are treated in the present, both socially and politically.