That's not how these two credit card networks work. You have card issuers and acquirers, both of these can be local, so it's not a big issue if you're cut off

That's not how these two credit card networks work. You have card issuers and acquirers, both of these can be local, so it's not a big issue if you're cut off from the world. It's more like a web of trust peer-to-peer protocol, so if a foreign entity removes you from the web of trust, you'll still be able to have transactions with anyone that still considers you trustworthy. That's probably the only reason why visa/Mastercard is so broadly accepted. Amex is run differently, and it's rarely accepted outside of the USA for example