Not in Philadelphia. We know very clearly where the Irish are supposed to go, where the Italians are supposed to go, where the Germans are supposed to go, and where the Poles are supposed to go. Everyone has their own neighborhoods and State Representatives and Parishes still. We do all get along fine though.
According to my relatives who live in Chester County, much of Philly remains stuck in a time warp. They mean it as a compliment, btw.
There's something sad about it, especially when there's so much talk of "diversity" in society today. There's a lot that's dishonest in that talk -- whether or not the deception is ill-meant. A diverse society usually has mechanisms at work underneath to make people more alike and bring them together. So yesterday's "diverse" institutions have to be kept alive with efforts that a down-sizing economy doesn't always want to make. Desires for success and assimilation and for stability and tradition come into conflict and, inevitably, something has to give way. So unless you can make a compelling case for separate Polish and Irish, German and Italian groups, they tend to get folded together into larger units.
But some people are quite angry about the closing of ethnic parishes, and the larger question of the fate of older ethnic communities. E. Michael Jones, originally from Philadelphia, has written about the effects of "urban renewal" on older Catholic ethnic communities in cities like Philadelphia and Boston. He is very angry and very much a partisan of old school Catholicism, and his book has gotten mixed reviews. Jones tends more to look for villains than for causes and for conspiracies than for solutions, and his paleocon view looks less impressive as time goes on, but his stuff may be worth a look, if a very skeptical one.