I would reschedule marijuana federally on day one if there's time. I might do it first. In Alaska it's been legal including home cultivation since 1970 due to a state supreme court ruling. I would do it like that and try to legalize home cultivation up to six plants. I would also coordinate with Canada on that so that if you're crossing to a legal province, they won't arrest you for personal amounts.
I would also coordinate with Mexico on whatever they need to prevent illegal drug supply from spilling across their border, or vice versa, and work out whatever kind of legalization arrangements seem sensible to them to implement in Mexico to reduce black market revenue. Sometimes the US has fought things like that, and sometimes countries don't want to legalize, I would talk to the president there about what strategies look right to her.
I would ask China to legalize. I think they would say no. They might arrest me one day if I'm elected, for bringing a vape cart, like Brittney Griner. #Free49.