If you are in fact being serious, Google 'indian reservations'
There is no threat of punishment keeping them there. They are free to live their lives anywhere in the US the same as any other US citizen. They do, unfortunately, have a higher percentage of poor people than most demographics, but being poor is quite obviously better than being kidnapped and tortured.
No one is trying to defend the history of the united states (there was this whole slavery thing after all), just the current united states. A past wrong does not justify a current one.
Maybe you think you can do better. Let's say you had a chance to be Andrew Jackson in 1830, and you're facing an American Indian crisis in Georgia. You have two options. The first is to let history repeat itself with the Trail of Tears. The second is to let the settlers and natives duke it out. Ultimately, the settlers will win and Indians are drived out anyways, but thousands more are killed in the process. The two groups are too different to coexist peacefully, and you don't have the authority from stopping people from moving to Georgia. Which option do you choose? Either way, history would remember you as a terrible person.
So, if one isn't facing a certain ethical situation, they can't make judgements about the response? This seems like quite poor reasoning to me.
Besides, why can't one accept that two different actions committed by different nations are both wrong? I suspect you're assuming that the posters are from the US too, which isn't necessarily true.