This is kind of interestesting, from the blog of reknown University of Chicago economist Gary Becker:
There is an ongoing debate among economists over whether social mobility is greater in the United States or Europe. The general evidence on this does not offer a definitive answer, but there is little doubt that most immigrants believe opportunities for themselves and their children are greater in the United States. This is why America is the first choice of most immigrants whenever they can choose where to go, and it also explains the different attitudes of immigrants in Europe and America. As Posner emphasizes, most immigrants, non-Muslim as well as Muslim, feel far more accepted in the United States than in Europe, are less segregated here in both their living arrangements and employment, and appear to advance more easily toward higher level jobs. As a result, they are less promising material for radical Islam, although clearly radicals are operating and planning in the United States as well as in Europe.
However, the British experience is somewhat disturbing to this thesis, for Great Britain is at least a partial counter example to our analysis. For British labor markets are very much like those in the United States; in fact, Britain has lower unemployment rates than the U.S., has equal labor market flexibility, and provides above ground jobs for Muslims and other immigrants.
I believe the main reason for the difference with the United States is that new immigrants are easily accepted in this country since it is a nation of present or past immigrants. Foreigners of all kinds have never been so welcome in Britain, and are even less welcome in continental Europe. So even under the best of economic conditions, immigrants in Europe do not easily integrate into the general society. Still I confess these vicious attacks on London subways and buses are not only awful, but I also find them difficult to understand.