I take it back, you've become one with the kool-aid.
Not only having the audacity to think America was the first to do that (lol - they based it on an old Greek model), but it's so western centric it would make a fascist blush, even though you don't have the same intentions.
But more than that, even hundreds of years before America existed, there were plenty of people who knew slavery - and especially the kind practiced in the USA at the time - was bad. There were countries where it was outlawed.
You can do all you want to excuse the hypocrisy of those founders, it doesn't excuse that they were just rich hypocrites who definitely knew better, but chose not to do better.