I realized something really neat a few days ago. It was kindof an a-ha moment, really. I forget why, but a bunch of people were sharing their ancestry. I'm from Scotland mostly, with a bit of Ireland. My Aunt has French ancestry, and some people had Finnish and German.
One said "It may not look like it, but I have African-American roots" (he's quite pale and has reddish hair).
At that moment I realized that "African-American" isn't a race at all. (This term, I won't lie, used to bother me, because it seemed to really be getting very vague about race. Personally, if I'm going to talk about skin colour, I use the colour words - "black" and "white". I feel they're neutral enough.)
"African-American", I realized, is a nationality. When the slaves were brought over they were separated from their true African nationality (which may not have even been a country name we'd recognize today) and when they final got rights and equality, they had no other roots to trace. All they can say is "I'm African-American", and that's quite different than being African.