Actually, the absolute heyday of racism and white supremacy in USA was probably just about 100 years ago.
However, it was based not on Biblical explanations, but on the science of the time, which was pretty uniformly outspoken about the inequality of the races and the superiority of the white race.
The only real scientific argument over this at the time was about which branch of the"white race" was superior to its other branches. Oddly enough, each of the scientists generally determined that it was his own branch. :)
The Bible documented the existence of a form of slavery in the bronze age Middle East. This was used by God Fearing men of faith who made their livings buying selling and working slaves to justify the thing their very lives and livelihoods depended on. The Bible mentioned it, therefore the Bible condoned it.
As to why the slaves were black Africans, rather than the more traditional Slavic peoples, after all that's where the very word slave (and me!) came from, why any devout Christian could answer that, black skin is the mark of Cain!
I give BenLurkin major major props for recognizing that his opinion is an opinion and that his expertise is not universal. Were that we all were so wise.
Mostly we all, each and every one of us, has a pretty much unlimited ability to justify doing whatever the heck we've set our hearts on doing, for God and Country, for the Children, because (my whackadoodle interpretation says) it's in a Holy Book, or whatever!