We have to remember that slavery was/is not a racial issue. Slavery is about power and economics; the power of one group of people over another. Israelites, Hittites, Eqyptians, Greeks, Romans, Persians all practiced slavery in one form or another; and each of these civilizations was, in turn, enslaved.
African slaves got from the interior of Africa courtesy of tribal warfare. The traders also realized that European traders were interested in cheap labor in the Caribbean islands, and Central and South America.
So, to lay blame to the founding of the United States is disengenuous. Not until slaves were freed in the mid-nineteenth century, did overt racism rear its head. People considered negroes ingnorant and uneducable, because that was their baseline of knowledge. What else would one expect, when the knowledge of Africa was limited to the ocean shores until the mid-19th century?
This discussion is being held in the light of late 20th and early 21st century perspectives. That is a far more egregious sin, than what and how people believed in the 17th, 18th, and 19th centuries. Since none of us were around in 1776, we can't be the judge of those who were.
Only in the last four hundred years has mankind moved toward science and technology societies. In fact, we weren't aware of the origins of the universe until the mid-20th century. Mankind has been around for about 3.5-to-4.5 million years. That's a long time to discover the human genome, viruses, the rocket, and oh yes, the gun.