Africa is a continent, not a little village in the jungle. It has one fifth of the world's land, one sixth of the world's countries, and one seventh of the world's population, speaking up to 3,000 languages depending on how you count. Africa is this big: kai.sub.blue/images/true_size_of_africa_v3-da3dd38e.jpg
"African-American" means born in Africa and a naturalized citizen of the USA. I have known some bonafide African-Americans, and every one of them was white and obviously of Dutch descent.
"Black" means only skin color. A black person might have come from any country (although I am told there is only one black person in China).
This confusion arose after the riots in the 60s. The whites asked the blacks what they wanted to be called and the answer was "black". The whites couldn't believe it was that simple and made up some other terms and eventually settled on this "African-American" bullsnot.