PSL are not trots.
PSL supports Cuba, Vietnam, China and the historical USSR.
PSL did branch from a trot organization, which might be why you think this. This is because most surviving leftist organizations in America post WW2 redscare were trot organizations.
Links to some random PSL publication articles to prove my point. https://www.liberationschool.org/category/china-2/
https://www.liberationnews.org/tag/cuba/
https://www.liberationnews.org/how-vietnam-defeated-u-s-imperialism/
Psl is a ml org. They are based on democratic centralism and the leninist principals of the second Internationale.