I’m not entirely sure about this, but I think it has something to do with the fact that European countries basically imported Muslims because they had a shortage of workers after WWII. Since they weren’t planning on the Muslims staying for a long time, the governments didn’t do much to integrate them into society. But then, the Muslims decided that Europe was the place to be and more of them kept coming. At that point, European countries wanted them to go back home because they didn’t want to deal with integration issues and the economy had stabilized. The immigrants had established families and homes, so they stayed put but still wanted to keep their culture. In the US, the situation was different because the economy was booming after WWII, and the country didn’t need a mass importation of immigrants for cheap labor. Another point: I’m not sure if this applies to other European countries, but France especially stresses the separation of church and state, moreso than the US does. So that just makes the problem worse, since Muslims mesh church and state together.