The thing of it is, the history of this poster's nation shows that it was doing the same thing contemporaneously with the burgeoning young nation of the US. They even fought wars (like the war of 1812), etc. for the "right" to do it here rather than let us do it ourselves. The assumption that the US should solely hold the guilt for the policy of the past is based on the ability to ignore the reality of the history of his own nation.
There is a reason that English is the official language of India and it wasn't because they were nice to them. There is a reason that Canada exists, and it wasn't without its own slaughter. France was spreading itself to this place as well, there is a reason that we were able to make the Louisiana purchase and it wasn't because France didn't participate in that same slaughter. There is a reason that they speak Spanish and Portuguese in South America, and it isn't because Spain and Portugal weren't participating in that same slaughter...
These people who try to judge were, at the same time the US was, spreading through the exact same actions.