Ramesh – You make an outstanding point and one I haven’t thought through that much. Being less enamored with notions of “national unity” than most, the first half of your hypothesis doesn’t frighten me that much. As for the increased reliance on the state to hold things together, I’ve got to think about that. It seems to me that was certainly what Al Gore had in mind in that conversation with Ward Connerly when Gore explained that the government needs to be the permanent barrier to racism — or some such.
Also, I would also say that lots of other trends exacerbate the unravelling of “fellow-feeling” as you put it (sounds dirty). Technology and the marketplace probably have probably done a lot more damage to the fellow-feelingness of communities than immigration. This is not to contradict your point, which I have to think about more, but merely to place it in its proper context.