What abuse given to the American Indians?
It is easier to answer this question in the reverse, being: What abuses were not practiced against Native Americans: The answer is None at All. Native Americans were used as slaves, target practice for guns and swords, starved, beaten to death, raped to death, biological warfare (introduction of diseases), medical experimentation, etc. In fact Hitler praised the US Government for its treatment of Native Americans (if that gives you an ideal of what inspired his actions, and its source).