Several. All small. The CPUSA, formerly aligned with the USSR, is basically a bunch of rather conservative Democrats who quote Lenin to each other in their spare time, The Revolutionary Communist Party is the biggest Maoist Party, which isn't saying much. The largest Trotskyist party, the International Socialist Organization, just disbanded over internal conflicts last month. These groups amounted to maybe 10,000 total. The biggest Socialist group is the Democratic Socialists of America, which as grown to 50,000+ since the 2016 Sanders campaign, has everyone from communists like me to anticommunist social democrats.
:)