The Free Banking Act won't stop them from doing this sort of thing in the rest of the world (US laws can't stop overseas activities, as much as the average American seems to not understand that America does not own all countries), which they've already been doing a ton of for years. And a lot of Steam and Itch's customers are outside the US. Sure, they may not be able to ban Steam from using Visa or Mastercard entirely, but they can still place bans on a consumer level, preventing them from using their cards to make purchases on Steam. Which could still be enough to put pressure on Steam.
I wasn't referring to it as a panacea for the situation, just one among several efforts, and obviously it wouldn't apply outside of the US. As much as folks like you would like to imply otherwise, the "average American", or at least in my case the average Midwesterner has enough on their plate to avoid worrying about the rest of the damned world. Even if I want to help there's barely a damn thing I can do about it here, let alone try to solve multinational political bull. So please, kindly take the snark and condescending attitude and shove it where the sun don't shine.