When conservatives say that they think the US is too "diverse" for such policies to work, take them at their word. They think that social democracy is fine as long as the benefits don't go to black or brown people. In fact, this was the essence the "grand bargain" that FDR struck to get the New Deal passed with reluctant support from southern Democrats - FDR was allowed to create redistributive programs so long minorities were systematically excluded from them (see Richard Rothstein's "The Color of Law" for examples on how this was achieved through federal housing policy). It's also the reason why the woman Reagan chose as the canonical example of the "welfare queen" (who herself is a fascinating character, see https://pictorial.jezebel.com/the-long-shadow-of-the-welfare...) was black.