Why is it in america so many people call mixed race people black when it is clear they are not fully black?

I feel like in America there is still this obligation to identify with one particular race. I feel like in America people struggle a lot with identifying people as mixed race.

For example, Obama is not black, he is mixed race. Yet people keep calling him the first black president.

I also notice this a lot among the black community. There are a lot of actors and actresses that are mixed race but yet people call them black just because one of their parents are black or they have natural brown skin.

For me coming from a country / background where mixed race people are clearly described as mixed race, I don’t understand it.

If segregations and slavery was abolished so long ago, why are people still using this “one drop of blood rule”? As a non- American I find it very odd and I know most of my non-American friends find it strange too.

Mixed race people do not have an identity crisis . They are human beings just like every one else. They are not white, they are not black. They are mixed race. Why can’t people just say that?

I even remember one episode of Top Model where the presenter was being so rude. She kept insisting that this model that was half-white , half-Asian, call herself Asian because she had many Asian features. I actually found that to be offensive yet no one on the show said anything.

Can you Americans please explain? Why do so many Americans still have so many race issues in the 21st century? Why the need to label people so much?

I come from a very multi-cultural background and country and so for me sometimes, I find it very odd the way on American TV people are so clearly labelled as black or white or asian or whatever as though it is a sin to call someone mixed race.

Why is this ? You can be honest.