In a way, France is a more modern society than the U.S. With its welfare system it offered migrants way more than they could hope for at home from day one. For the second generation it must have been even easier. They got the level of freedom and the standard of living head and shoulders above than that in their cultural motherland. They got French passports. Even on the lower steps of the social ladder they were doing way better than their brethren in Algeria or Mali. They still didn't integrate. Who's to blame?