Slavery existed in the Americas long before Columbus ever sailed.
Slavery in the colonies which became the United States was more humane than slavery in the rest of the Americas.
It existed in the world most everywhere.
It was Western civilization and Christianity which ended most slavery, until recently, when Islam started re-asserting slavery in many places.
Islam use to make Christians slaves. The slaves from Africa were treated worse. The males were castrated and few survived the brutal operation.