Please do explain the differences in approach between the Nazis and the British and American governments when it comes to colonization and the persecution of undesirables.
The only real differences are of degree, and since that was pretty much a result of staring down the business end of the losing side of a war, it's easy for me to imagine us acting similarly. For instance, had Japan invaded the contiguous US and were approaching our internment camps and Indian reservations, the decision to convert them to kill camps seems like something we would have done.