Hi Rachel,
I have a number of friends who are black, and some of them prefer AA and some prefer black, so...I don't think there is a "right" and "wrong" with that in general--it's more individual preference.
I prefer black personally, when I do not know where someone is from, for the very reason you say. I have a Senegalese friend who does not like being called AA at all. She says her culture is nothing like the AA culture, and she is not American. Just b/c she lives in America does not make her American. She prefers being called Senegalese, but if someone does not know her, she would rather be called black than AA.
I think it can get confusing with today's diaspora too. I mean, what about a black couple who were born and raised in Germany and move to the US and have a child. Is that child German-American, like white children of German parents would be called? Or is he African-American, because he is black, thereby totally negating his German background...there si a crossover of race and culture which can get confusing. Or is he a black German-American, in order to better clarify race and culture at once?
I would say that for me, I do not think there is a right and wrong, and so I think about what I am trying to say with the label. I realize my Ethiopian-born son (which is how I say it) will be perceived as AA, and I realize he will become part of the AA culture as he grows, BUT his background is not AA--his background and culture is Ethiopian, and I don't want that to just fade away as he gets pegged solely by his skin color.
How's that for a straight answer?!

Teranga
mom to 2 bio children and 1 child adopted from Ethiopia