Trans-Saharan slavery existed before trans-Atlantic slavery and ended (officially) long after America fought a war to end it trans-Atlantic slavery. Slavery still exists in many parts of the world, including Africa. People who come here are more aware than you think. I have friends from communist countries and they are also aware of the Marxist roots of America's political left. Perhaps you should travel and see for yourself. It's not 1865 and no one alive today experienced it.