There has been little coverage in the American press until today's NY Times article.

Burning cars as a form of protest is not unusual in the largely immigrant, working-class neighborhoods. Unemployment rates there are 30 percent or more, while the national rate is 10 percent. More than 20,000 cars have been set ablaze in France so far this year, according to a government report cited by the newspaper Le Figaro.
The periodic violence highlights France's failure to integrate immigrants into the country's broader society, a problem that has grown in urgency as the unemployment rate climbs. Most of the country's immigrants are housed in government-subsidized apartments on the outskirts of industrial cities. They benefit from generous welfare programs, but the government's failure to provide jobs has created a sense of disenfranchisement among the young. A highly observant form of Islam has grown popular among the mostly Muslim population.

And just noting from the Guardian above:

Not for the first time, the unrest has highlighted tensions between wealthy big cities and their grim ghettoised banlieues, home to immigrants from the Maghreb and West Africa who have never been fully integrated into French society and have become an underclass for whom hopelessness and discrimination are normal.

The parties of the right will naturally focus resources on the richer areas that support them. Leftist parties and policies attempt to ameliorate the situation when they are in office, but the swing voters reside mostly in the middle class and thus the balance of political power militates against the poorer areas.

This effect is most pronounced in large cities because community feeling is always lower across such a large electorate. Once you add in some elements of race and culture clash it gets increasingly difficult.

I often feel that this is one of the unspoken challenges of the coming years for the left. How do we build the sense of community in an increasingly atomised world? It is only with a sense of community that a mandate for "the common good" can be established.