As a Brazilian, understanding how Americans classify people into races can be quite confusing.
As far as I know, the whole human races idea came up sometime during the XVIII century, and it sounds rather problematic and unscientific to me.
I mean, classifying people by nationality make a lot of sense, but dividing them into races seems rather random sometimes.
I am not agains the concept per se, and I understand it can be useful, I just find it hard to make sense out of it when I read some threads.
For instance: Spanish people are not white, right? They are Hispanic. What about the Portuguese?
Another one: Northern Italians are surely white, aren't they? What about Southern Italians?
I could probably come up with a few more of these examples.