From the article :
At least this article (you should read it) reports with partial truthfulness on the real numbers of Africans who were enslaved in the U.S. : about twelve million Africans (the Times here just says "millions" without specifying 12) were shipped across the Atlantic as slaves up until 1888, when Brazil finally outlawed the importation of new slaves (the U.S. outlawed the slave trade in 1807). Of those 12 million, fewer than half a mil (estimates vary) would up in the U.S. Most went to Brazil (>10m) and the Islands. Of course, one doesn't see the words "legacy of slavery" and "Brazil" too often in the same sentence.