The US goverment can't make porn illegal in another country. A US owned payment processor can force other stores in other countries that uses their service to save money to ban porn as well. You're just advocating for giving governments of wealthier countries more control over smaller ones. I say no thanks to that nightmare scenario.

Why don't you prove your government can do their job and prevent payment processors from being such massive monopolies and maybe I'd trust that they won't immediately abuse their power.