There's a world of difference between European immigration problems and American immigration problems.
While American immigration problems are primarily economic and center around illegal immigration, the main issue with European immigration is cultural, although there do exist concerns due to the massive welfare states of most European countries. Europeans are simply not used to the concept of extremely foreign cultures- even among Europeans, consider, there have been only in the last 20 years or so massive sectarian and ethnic conflicts (Yugoslav wars, continuing Northern Ireland BS come to mind). Large populations of immigrants from the Middle East; people who don't speak anywhere near the same language, don't follow anywhere near the same religion, and aren't exactly running with open arms to convert and lose their own culture. Also, most European immigrants are legal- Germany became a beacon for Turkish immigration with the Gastarbeiter program of the 70's, for example, and Sweden has a large problem because of their lax definitions for refugee status, and France has a lot of immigration from its former colonies, etc. (that's not to say that there are no illegal immigrants in Europe, Italy, France and Britain in particular have issues with illegal immigrants from the Middle East and North Africa).
It's just impossible to compare.