Thanks for you comment! After all, the concept of "ethnicity" is highly debated and numerous definitions exist (just have a look at the wikipedia article). Many European countries don't even ask for "ethnicity" in their census; cultural minorities are often rather defined by their language because this is what practically matters regarding things like school, traffic signs, offices, court, etc.

Therefore I find it pretty odd that in the USA the idea of a uniform European "ethnicity" - largely defined by skin color! - is still very common and even officially practiced. I remember how I had to fill a form when entering the USA which asked for my "ethnicity". I was flabbergasted and just ticked "unknown" or something like that because I didn't want to identify myself as "Caucasian".