Thanks for the clarification, @YeOldeOke. What do the "stricter standards" relate to, though, if not sales to minors? I was chatting about this in Discord and American vapers don't seem to have any problems with Visa/Mastercard there. Is this because their processors are willing to go the extra mile?
I'm not 100% sure exactly what it entails, but e-cigs get dumped into high risk with tobacco, porn, gambling etc.
To state it simply, primary concerns for merchant processors include increased possibility of fraud and/or excessive chargebacks. Merchant processors go to great lengths to avoid both of these. Inside the USA, where merchants are issued social security numbers and employer identificaiton numbers, it's easier to locate a merchant in the event of fraud. Since social security numbers are not issued outside of the USA, US banks will typically not underwrite merchant accounts for businesses outside of the USA, so non-US merchants are forced to use a non-US merchant processor.
Maybe why they are easier on it in the US, dunno. Or they already pay high risk fees.