Reihan Salam makes an excellent point:
As Ed Glaeser and Alberto Alesina have argued, it seems that ethnoracial fragmentation cuts against redistribution — taxpayers are reluctant to subsidize members of outgroups, a gut instinct that is easily characterized as racist. But perhaps this impulse is a useful corrective, and one of the virtues of diversity — i.e., perhaps greater homogeneity leads taxpayers to overinterpret a kind of nationalist sameness, thus leading to higher levels of redistribution than are in fact desirable. Now, I don’t think this is obviously true, but it’s no less plausible than the other story, namely that the interrelationship between extreme homogeneity and social democracy is an unambiguously good thing.
My take is that the kind of homogeneity and conformity necessary to generate the sense of solidarity that leads to popular, high levels of redistribution ought to be unattractive to liberals, who are either cosmopolitan pluralists or not really liberals at all. Add the fact that that there are superior feasible policy alternatives to lavish state-provided social services — deregulated labor markets, actual markets in insurance and health services, higher rates of growth, etc. — and American liberals really ought to stop trying to wish Nordic levels of solidarity and redistribution into existence, and instead just get with the program of promoting actually feasible market-based reforms.