The attempt to account for America’s anti-socialist exception has sustained a thriving academic cottage industry among historians, sociologists and political scientists over many decades. As long ago as 1906, the German economist and sociologist Werner Sombart was asking: “Why is there no socialism in the US?” The answer, he thought, lay in the success of capitalism and the extent to which American workers identified as a result with the prevailing social and economic settlement. “On the reefs of roast beef and apple pie,” Sombart wrote, “socialistic utopias of every sort are sent to their doom.” There were other factors at work too, Sombart argued. America had no feudal past, which meant that workers there felt the political system was largely responsive to their needs, in a way that their European counterparts, who’d had to fight to achieve the franchise, did not. Greater social mobility led most Americans to value self-improvement over collective action, while the open fr...