I haven't been following closely, recently, but literally the first one I checked has no check on residency [0], which is enough to bring it under SEC jurisdiction if the sale goes over other thresholds.[1]
Sales before and after the bulletin are subject to the same laws.
It was totally legal for US residents to participate, as far as I know. I believe almost all the securities-law obligations resulting from the sale are on Tezos. (Not a lawyer.) The only obligation on buyers might be that they can't resell it without being guilty of selling an unregistered security themselves.