FRSO seems good on most things, but supports "upholding past treaties" with native Americans, which is somewhat of a red flag. PSL seems good but I've heard claims that they're not that good on the settler colonial issue either and lack proper democratic centralist structure. I don't know much about the WWP, but their 15 point programm doesn't mention landback at all. I know next to nothing about the other socialist parties/orgs on the US, so I can't give my opinion on them
PSL is an explicitly ML org as far as I'm aware. It's ML, upholds Stalin who is part of their required reading, and is dem cent in structure aside from a few adaptations to allow critical issues to bypass command structure to avoid local abuses.
Willing to hear otherwise but I've never heard members or former members say otherwise.