A few things that are accessible within the USA include:
- Participating in mutual aid programs
- Campaigning on the local level, including for positions like poll watchers
- Making your voice heard in community events in general
- Joining your local DSA, networking
Leftism isn’t about winning, that’s the part you’re missing. If you’re just doing what you can to win than you’re no different to and will fall for the same things as a fascist. I remember hearing “leftists are addicted to losing” and what makes that quote especially good is that it came from a guy who later outed themselves as being a fascist infiltrator once they no longer needed to convince people to vote Democrat.
Marxists don’t care about winning. That’s idealism. What we want is an improving of material conditions for the working class.