It's a hazy landscape, for sure... but even though there is discrimination in the US, maybe it's not as severe as in France. The rioters in France seem to be mostly poor Muslim North Africans (crossed and intermixed with thuggish bored youth) who are upset because French society treats them as second-class citizens.
There is a more distinct line drawn between these North Africans in France because there are so many (geographic proximity) and in such ethnic concentration (recent immigrants). Apparently, France doesn't have a great track-record with integrating other cultures (refer to the "preserve French language" obsessives). I'm no expert, but from what I read and hear... that is the case.
The US, on the other hand, at least pretends that one of its guiding principles is the great melange. Melting pot and all that.
It seems that the riots in France are a mix of pent up anger, opportunism, envy and racial/religious hatred. It's a mob scene. I have no sympathy for mobs of any type... be they riot-geared police, looting gangs, environmental protestors or Christmas shoppers... so maybe I'm missing some important issues.