Yup, disease killed a lot of Native Americans. Hmm, where'd that disease come from? Why did it spread to them? It couldn't have been because the Europeans came to visit, could it? Then later, our own USA "manifest destiny" policies, could it? Point here is that the "white man" was still the cause, albeit indirectly, of the wiping out of the Native Americans. Discounting the numbers game, the US military killed off a lot of civilians in WWII. We don't play that blame game with our own military do we? Some were accidents (we bombed the wrong thing, e.g.) and some were deliberate (Hiroshima and Nagasaki, e.g.)
Now, I'm not comparing the US Military to Hitler's regime directly, but both were responsible for civilian deaths. The reason one is still blamed is because one is "evil" and the other was acting to quell the "evil."
Yup, the US corrected ourselves with the slavery issue. It only took a 5 year war that cost 100,000's of lives... I guess since we were mainly killing ourselves, we absolved ourselves of blame?