Slavery existed in the world long before Europeans came to North America, and continued to exist in the world after the Emancipation Proclamation and ratification of the Thirteenth Amendment to the U.S. Constitution.
It was, is, and will be, a morally abhorrent practice no matter the skin color of the slave or slaveholder.
Something in the neighborhood of 12M slaves were shipped across the Atlantic from the 15th to 19th centuries. At most 5% of this number came to what is now the USA. Largely because North America was the most distant market, limiting the number of trips a slave ship could make in a given period and thus profits per year.
Roughly the same number were transported across the Sahara and shipped across the Red Sea and Indian Ocean from the 7th through 19th centuries in the Arab slave trade. Which probably still continues today, on a greatly reduced scale.
So at most 2% to 3% of Africans traded off the continent came to areas now included within the USA. Yet somehow this vile practice has become sterotyped as peculiarly or even uniquely American.