Every society on Earth exists as it does because it destroyed much of the previously existing landscape and natural inhabitants, most definitely including the Native American societies. If you read Over the Edge of the World, a fascinating book about Magellan's voyage around the globe, you'll find that as he traveled the straits at the southern tip of South America -- the most miserable, cold, dreary, and awful environment that could be imagined -- he met a miserable and starving aboriginal tribe: a tribe that, it turns out, had been pushed all the way to the tip of Tierra del Fuego by succeeding waves of "native" migration across the land bridge from Siberia to Alaska. The sin of the United States is not original with the United States: it is the sin of every society.
> But some level of responsibility nonetheless (and when adding up the small responsibility of each current member the responsibility to do something as a group to rectify past wrongs may become quite large indeed).
You could smuggle an elephant inside that parenthetical clause. For starters, how specifically is one to "rectify past wrongs" that were committed against people who have been dead for hundreds of years? And are the remnants of those societies that still exist today also obliged to "rectify past wrongs" against the people they aggressed on even farther in the past?