Not a peculiarly American practice: every civilization, and probably every pre-civilized agrarian society had slavery or slave-like castes.
What is peculiar about slavery in the colonies of European empires and in the US is that it arose in a society that had effectively abolished slavery. From at least the 1300s onward, there were no slaves in Christendom outside of the Eastern Empire before its fall in 1453, where the Greco-Roman institution persisted (and Romania, where Gypsies were kept at chattel slaves until the 19th century) until the Portuguese sailed down the coast of Africa looking for a way to get to the Orient not controlled by Muslims, and found that there were trading opportunities in West Africa, but that the most valuable thing the Sub-Saharan Africans had for trade were other Sub-Saharan Africans.
Arguably, the institution of slavery as found in the colonial Empires in the New World was, like the slaves, an export of Africa. Indeed, the first chattel slave in what became the original 13 States was an Angolan John Casor, whom a Virginia court found was not the indentured servant of another Angolan, Anthony Johnson, but his property. The Africans who landed in Virginia in 1619, whom the Left makes so much of, were treated as indentured servants and freed after the standard term of indenture, there being no basis in English law for chattel slavery. (The Virginia court that enslaved Casor was creating a new precedent, which, unfortunately became established law.)
Everywhere else, slavery had been there since ancient times.
The other peculiar thing about slavery as practice by Europeans and Americans in the 16th to 19th centuries is that we were the one slave-holding civilization besides Japan to abolish the practice, and when we abolished it, we obliged everyone else we came in contact with to abolish it, too -- that aside from here where we fought a Civil War to get it done -- was mostly the work of the British starting in 1830. Besides abolishing slavery inside their Empire, they had a part of the Royal Navy devoted to stamping out the Atlantic and West-African slave trade, which cost them so much money that the debts they ran up doing it were only paid off in the middle of the 20th century, and used "gunboat diplomacy" to abolish slavery in the Muslim world as well (though it's not entirely clear how well that abolition actually took).
