When you point out that other countries grow as fast (or faster) than the US does and innovate as much (or more) than the US does, all while having higher tax levels, lower poverty, and lower inequality, eventually partisans of laissez-faire capitalism come around to say those countries are all one-off exceptions owing to their homogeneity. Taken as a political argument, this is fair enough: I have little doubt that the existence of a good number of poor Blacks and, more recently, Latinos coupled with a viciously racist society makes it politically difficult to aim for lower inequality. As a policy argument, however, it doesn’t really make sense: more money makes you less poor no matter your skin color and the egalitarian projects less homogeneous countries do try (e.g. public pensions, child benefits) work like a charm.
There is one actually meaningful policy argument when it comes to public policy and homogeneity, however. You can find this argument littered throughout anti-socialist texts during a period where heavy amounts of direct government provision of all sorts of goods was still a more commonly sought-after thing. It goes like this: in a more homogeneous society, direct provision is more viable because people’s specific needs and tastes in goods are more uniform; in a more heterogenous society, such provision will be much less successful because needs and tastes are much more varied.
This is a decent enough argument, but it obviously doesn’t reach cash transfer income, which recipients can spend on whatever they’d like. More interestingly, it seems that those on the side that like to make the vague gestures towards homogeneity are the most likely to favor more direct government provision of goods.
Food stamps are an excellent example of this. My position, and the position of any serious leftist I know, is that food stamps should be converted into a cash benefit program. Not every person with low market income needs more food (they may have other ways of getting that cheaply) and many could use those resources for other important things like paying bills, buying diapers, and so on.
It is generally the conservative, however, who not only balks at the idea of converting food stamps into a cash program, but who actually seems to want to make the food stamp program even more restrictive. It is conservative states that are trying (it seems mainly illegally) to greatly restrict what people can purchase with food stamps. These restrictions bring the benefit much closer to providing a uniform bundle of specific goods, which is precisely the kind of thing that is not supposed to serve a heterogenous society very well. Where everyone in a country basically has the same food culture and eats the same things, a very restrictive bundle of food may work perfectly fine (as it matches everyone’s tastes anyways). Where people in a country come from very different food cultures (some vegetarian, some kosher, some halal, and many derived from the national cuisines of all sorts of other countries), this does not work nearly as well.
Thus, on a policy level, the homogeneity insight is not without its lessons. Finland’s maternity package, which delivers a specific bundle of baby clothes and other essentials to expectant mothers, may not be viable here where preferences in baby clothes probably vary much more, both because of cultural variation and even variations in regional climate. It’d probably be smarter to give expectant mothers a $500 check instead, which incidentally is an option in Finland anyways in lieu of the maternity package. This lesson, then, is not a lesson against egalitarianism in heterogeneous cultures, but a lesson for much more cash-driven programs, which the conservative bloc that raises the homogeneity arguments are also paradoxically against.