Why are americans so obsessed with race?

I am a south-eastern european. Why do americans always have to ask questions like "Were romans/greeks white?" or "Are italians/spaniards/romanians white?"
Like....come on. Just leave the rest of the world out of this annoying attempt of trying to claim different cultures and histories just because you are all confused by your history and want to be proud of something even though you haven't worked for it. This is my explanation for it, but I am open to another explanation. What is the point of dividing everything into races to claim it as soon as that thing is interesting to you?
As soon as a movie or show or game portraying a culture is released, you're all hungry to claim it and then you get bored and move on to the next thing. It is tiresome for all the other people in the world.