>What is the difference between the Communist Party of the United States and the Party for Socialism and Liberation?
Despite being a Marxist-Leninist party, PSL has never quite been able to shrug off their origins in the Workers World Party. It's an old saying that all of the Trotskyists who were influenced by Sam Marcy's ideas became neoconservatives by the 1980s and 1990s, and this came to a head in 2004. Chapters are mostly confined to major cities (and have sometimes been referred to as cults on account of the sheer number of youth organizers and resulting allegations of sexual abuse, as well as the party's education program spending organizational resources on social media "like" policing), but they've been slowly expanding into the hinterland. They are the second largest left wing party that are able to participate in elections (first being the Greens). AFAIK dues are the most expensive of any party in the US. I'd say that with PSL you either go hard or go home, but most of those dues probably go into Gloria La Riva's farcical presidential campaigns. They've been pretty good at organizing protests locally, however; two organizers in Colorado got v& last year which is unfortunate.
CPUSA on the other hand are the OG party full of boomer communists. They are participating members of the IMCWP, which means they ostensibly have working relationships with AES states like Cuba, Vietnam, and China. Some of the oldest anti-communist legislation in the US still applies to them, barring members from re-entering the country and running candidates on virtually any level of government. Despite this I hear they're pretty comfy and normie. PCUSA split from them in 2016 because they weren't on the soviet larp bandwagon. Since the Trump-era they've tentatively aligned themselves with DSA/Justice Democrats; the loudest voices in the party seem to be Browderites (look into CPUSA's "Popular Front" strategy during the Great Depression, "Communism is 20th Century Americanism" type stuff), but without any of the mass organizations they had 80+ years ago. This didn't stop them from publicly showing support for Biden (awful!). They reestablished the Young Communist League as of last year, and I hear they're looking to challenge the laws barring them from running candidates again, which sounds nice.