Both can be (and are) true, while the Europeans and later Americans did many things that would now be classified as genocide and ethnic cleansing, the majority of the native population simply died inadvertently of diseases. It’s actually unlikely that the Europeans would have been able to so thoroughly conquer the Americas if the native population would have survived the first wave of diseases.
If you want the US to act in line with the Paris agreement, if you want a humane healthcare system, if you want effective action against police violence, if you want the US to stop supporting a possible genocide, it doesn’t matter what you vote next election.
This is just a fact, you can do with this fact whatever you want, vote for the least bad option or stay home, but that doesn’t change this truth.