Slaves still exist today, right now, all across Africa, India, Middle East, South America, and 'almost' all of Asia.
And many of them are owned by Black slave-masters. It been like that forever.
But American political propaganda says slavery only occurred once in history when Blacks were sold by Blacks to Europeans who in turn sold them in America. Slavery only happened to Black people and slavery only ever happened in America.
Slavery has happened all over the Earth and is still happening today. To say that slavery is somehow 'unique' to America is insanity.