Aaah... slavery? The slave trade was abolished in 1807, and slavery altogether in 1838. In the British Empire, as was.
The Constitution was a great document and truly groundbreaking. I honestly believe that. Unless you had the misfortune to be born black before 1865, of course. Then it was a little less sparkling.
The point is this. Ethnic cleansing and slavery as operated by the British was evil. The US had the opportunity to shape its own destiny the moment the Declaration of Independence was signed, and could have outlawed both. It didn't. Blaming the British for events on sovereign US soil is a little too convenient for my liking.