African or american? not african-american!

Why do Americans of African descent go by African-American?
Americans of Asian descent do not go by Asian-American and those of European heritage do not go by European-American.
We are all the same. We are all American. There is no in between. You are either American or not, right?
I hear about how some blacks claim they are treated unfairly (I disagree, but that is another topic), but don't you think if they want to be treated the same that they would go by just plain old American?
Now, don't get me wrong, I am not racist in anyway. But I am an American and I believe we are all the same. is it normal to feel this way?