A huge cataclysm of some kind wrecked North America and other continents at some point during the early 1800s, changed the natural landscape, and wiped out many of the people living there at the time. People of all colors and cultures were always in the Americas. The bands of nomadic survivors from the cataclysm are what have been called "Native American" as a way to hide the ruins and other evidence of high civilization that is all around us.
Jon Levi: https://www.youtube.com/channel/UC5vXBfxN7rxKeJHJxS8dNDw
Also, most black slaves were native to the American continents and surrounding islands, not shipped from Africa.
UB TV: https://www.youtube.com/channel/UC7QLYJht9OUYIwZI_TTyjiA