It’s almost cliché to say that America is more divided than ever. Countless columns, books, and news segments draw attention to the issue. It fuels the Right’s National Divorce meme. The Left blames social media for fanning the flames of division and fears we’re heading to civil war. Ironically, polarization may be the one political issue everyone agrees on. While backed by clear evidence, our political divisions pale in comparison to our broader, shared monoculture. The political divisions are obvious. Polarization leads some, particularly on the Right, to conclude that America is undergoing cultural balkanization. These voices insist Red America...