You left out the bit that people who looked like the Slaves in their countries of origin sold them to White Men.
Here's a clue, bub. Slavery has existed For Millennia. Slavery or Serfdom has been the most common condition of existence for the majority of people who have ever lived. It is only since the advancements developed during the Industrial Revolution were combined with the Individualist Values of Western Civilization that slavery has been abandoned in some of the world. It is still practiced in quite a few places outside of Western Europe, the U.S. and Canada. Perhaps your energy would be better used opposing actual slavery that exists today instead of reliving something that the U.S. fought a war in which 700,000 died in order to eliminate.
Racism in America didn't die with the Civil war and the freeing of the slaves.
"Racism" didn't even start with the Civil War. No one ever even heard of "racism" in America until after WWII. Before that, if someone said, hey, you preferred that guy to that guy, Americans, like the rest of the world, would say, well, of course, that's my brother. We're more closely related. Of COURSE!