I just read an interesting empirical study on Jewish feelings of outsiderness in the United States.* The good news is that most Jews don't feel like outsiders in the United States. So yay for that! But the interesting part of the study, to me, was what accounted for the sentiment. In general, Jews who lived in areas with many other Jews and who had many Jewish friends and acquaintances were far more likely to say they felt included as Americans. By contrast, Jews who were more isolated from other Jews and had fewer Jewish contacts were more likely to feel that they were outsiders in America. Since most Jews live in areas with relatively large Jewish populations, that means most Jews feel relatively included in America.
To me, this finding is quite intuitive. But it does clash with a narrative some forward, that insularity and particularism amongst minority group "ghettoizes" them and prevents their integration into the American mainstream. It turns out that story seems to be wrong. Rather, when a member of a minority group has surrounding structures demonstrating the normalcy of their peers (that they're average, non-exceptional members of the community), it is likely to reinforce the message that there is no conflict between being a member of the minority group and being an American.
The upshot is pluralist. If what we're going for is a polity in which people of all backgrounds feel welcome and included as Americans, the right strategy isn't to try and breakdown particularistic group affiliations. Rather, these groups are essential to the mainstreaming process, because they promote feelings of normalcy and non-exceptionalism amongst the minority group, which in turn renders the surrounding culture less alienating.
* Becka A. Alper & Daniel V.A. Olson, Do Jews Feel Like Outsiders in America?: The Impact of Anti-Semitism, Friendships, and Religious Geography 50 J. Sci. Stud. Religion 822 (2011).