One possible answer may be that America is simply too religious. As Andrew R. Lewis and Paul A. Djupe of FiveThirtyEight explain:
To understand the relationship between socialist values and religion, we used the 2013 Public Religion Research Institute’s “Economic Values Study.” As part of the survey, respondents were asked how much they agreed with a battery of statements regarding economic values, including “It is the responsibility of the government to take care of people who can’t take care of themselves,” The government should do more to reduce the gap between the rich and poor” and “The government should guarantee health insurance for all citizens.” We combined these into a “socialism scale,” the results of which suggest the average American is just left of center.
The conventional wisdom is that the individualist, evangelical style of American religion is a strong antidote to socialism. If faith alone can lead you to salvation, then efforts to reshape society are beside the point. But the animosity between them has been more pointed, especially regarding so called “Godless communists” who portrayed religion as the “opiate of the masses.” In these data, those who agreed that social problems would be resolved if enough people had a personal relationship with God were 20 percent less socialist than those who disagreed. A worldview that pits faith directly against collective action explains clearly why collectivist efforts have traditionally foundered in the U.S.
Based on this data, it’s not surprising that the Americans who are most supportive of socialism are the “nones.” As Lewis and Djupe note, “Nones are 10 percent more socialist, on average, than religious Americans.”