There’s a growing body of evidence that even if diversity— the kind that results from immigration — once made America stronger, it may not be doing so anymore. Robert Putnam, a liberal sociologist at Harvard, found that increased diversity corrodes civil society by eroding shared values, customs and institutions. People tend to “hunker down” and retreat from civil society, at least in the short and medium term.

I think the real culprit here isn’t immigration or diversity in general, but the rising stigma against assimilation. Particularly on college campuses, but also in large swaths of mainstream journalism and in the louder corners of the fever swamp right, the idea that people of all backgrounds should embrace a single conception of “Americanism” is increasingly taboo.

Anyone of any race or national origin can be an American, but it requires effort and desire from both the individual and the larger society. There’s a shortage of both these days.