"My question is about the recent period. Do race and ethnicity remain important tools of bourgeois hegemony even today?"
I would say they do. The U.S. remains a largely segragated country. Suburban life (defined by flight from the more integrated cities), which defines life for most Americans (both in and out of the suburbs), is a fact on the ground and continues to shape American consciousness. I have a dim memory that Marx once opined that socialism would not be possible in the U.S. before it resolves the race question. I think he was right.
Joanna