The card issuer ultimately decides and I suspect it varies. These things can be pretty annoying internationally though, I've had the opposite problem that Canadian gas pumps won't take my US credit card and I have to pay inside - I think because for whatever reason Canadian credit card terminals want a signature slip every time I use my card, which based on cashier confusion I take it is unusual for Canadian issuers. Mexican credit card terminals don't do this, so there's something more inconsistent than just international transactions, I assume it's an irritating interaction of the network trying to line up the schemes in the various countries.
Amusingly debit cards tend to be less of a pain this way since the North American countries are mostly on the same interbank network and the rules have changed less over time.