Yes, slavery was alive and well in America 180 years ago and George Washington owned some. Still, the descendants of those slaves live far better lives in America than people in Africa.
Look what happened to Liberia when some of them went back.
That was something James Brown recognized and was grateful for. He (and others who made it) said it's sad and 'sucks' what their ancestors went through but that they (the descendants) were much better off than if they'd stayed in Africa.
Even when James Brown went to Africa for a concert coordinated with Ali/Clay's fight, he said he was more grateful to be able to live in America.
The problems in Africa in the 20th century were part of it. The potential for personal growth and wealth in America was the other part of it. He said 'no place else' could a man go from so little to so much.
Here's some of it in song (the fight concert was 1974, this was 1968).