Though, that goes for all of the US. America is built on top of Native Americans, and on the backs of slaves.
Not to get off topic, but the entire world has been built on the backs of slaves. Every freaking country. Not only America as is so popular to assert these days.
Yeah, but we were the first country founded on democracy and with the phrase, "all men are created equal" in our literal declaration. At some point, we have to either stop claiming we're the best ever OR stop going, "yeah but X country did it too", when our flaws and mistakes are pointed out.
I never thought there could be anything that would get me to stop cheering for the Miami Dolphins, but Tom Brady in a Dolphins uniform might do it. If by some chance it happened I'd cheer for him to fail.
At the time, slavery was common all over the world. However, it was the Western World, which the U.S. is apart of, that first made slavery illegal. So in that respect, yes, we are the best. Jefferson, and many members of Congress, had created a passage in the Declaration of Independence talking about the immorality of slavery. However, and even though he had actually argued in court for the abolition of slavery, they decided that keeping this passage in the Declaration would stop the movement. He, and many others in Congress, thought that the "all men are created equal" passage would, in time, make sure that slavery went by the wayside. They were right...but they were also wrong in participating in slavery.