The rest of the world is like that. Black and mixed are a different classification.
and its the main reason black folks in other predominantly white societies are worse off than American blacks. the one drop rule though it originated based on racial hatred, was actually a blessing in disguise for black folks in America. while blacks in Brazil have been divided based on differences in skin tone, blacks in america have more or less viewed themselves as one people even with differing levels of white admixture. this has allowed for greater unity, greater political clout, and equal rights in law faster than our cousins in latin america who didn't subscribe to the one drop rule.
just think. how the hell does america have a "black president" with only 13% black population than brazil which has a "black population" of over 50%? because "blacks" in brazil don't view themselves as the same or having the same interests. the white minority has used divide and conquer tactics to keep the majority down while they have all the power and control.
now i'm not saying black folks in america have power and control. but we sure are better off than any other black groups in the Americas. especially those in Brazil who outnumber whites in that country yet have almost no political power.