Only Catholics and Episcopalians (to a lesser extent) care about what the Pope says. Well, he's obviously still an important spiritual leader for all Christians, but no other denominations actually are required to abide by what the Church says. Even then, the people saying the Pope are infallible so Catholics have to agree with this are wrong. A lot of Popes before Francis said the exact opposite of what he said here, that Catholics should beware of Marxism and Socialism. If they were always infallible, the statements would be contradictory and something would be seriously wrong. The Pope is only infallible when speaking Ex Catedra, which AFAIK has only happened twice (declaring the Assumption of the Virgin Mary unto Heaven and the Immaculate Conception, i.e. two fairly specific doctrines, not social mandates).

TLDR: What the Pope said is not exactly binding for anybody, much less the most reactionary Christians in the US. It's a step in the right direction, though, so still welcome.