While I am not in favor of slavery, and this may sound cruel, but American blacks should learn that it was slavery that gave them life in the USA. Otherwise, they would be in some African hell-hole, chucking spears.
For white Americans it led to something of an unintended travesty.
The more I read of Southern US history, the more I see that there was more white on white slavery than white on black slavery.
They would have as likely been sold elsewhere, certainly not as nice as America. Their own people sold them in slavery as often as not. Who hasn't heard the story of the princess who sold her people off until there were not enough for the slavers? They took her last.
If I could go back in time to the moment someone first thought of bringing slaves here. I would put a bullet in their head.