I think a president and enough political supporters could turn the US into a socialist or communist state, a president like that could at least make some incremental changes, but with the elections and state functions so controlled by capitalists and bourgeois interests it seems unlikely in the US political climate. I don't think it's impossible though and we should use all means possible to help, but issues we face such as climate change and wealth inequality require more substantial changes that aren't likely to be passed and implemented quickly enough within the current structure to adequately address them in time.