I think there are a few big issues: Because of the mutt stereotype (which is somewhat true, really) many can't trace their origins or identity to one particular ethnic group in Europe. Many can, but there is still a large chunk who cannot, and would have to choose or split their identity between 2 or even more groups. There's also the lack of cultural carryover, some regions and families still practice ethnic holidays and such (many places in the midwest having Oktoberfest being the obvious example) but many people simply don't know or practcie their cultural traditions anymore. A final big issue is the fact that unlike Europe, where each ethnic group has one or mroe countries or regions where they can say they came from or still reside in, the US is very heterogenous as far as distribution of different ethnicties, White and otherwise, and the elite surely don't care who or where we are as long as they can squeeze us and keep us under their thumb.