Apple Pay international transactions

If you’re referencing the ability to send money to others using “Apple Cash,” it appears that the feature is only available in the United States as of today.

See feature availability here: iOS and iPadOS - Feature Availability - Apple

If you’re talking about using Apple Pay to purchase something from an international merchant, you’d be able to use Apple Pay with any retailer that takes it online. You might need to make sure your credit/debit card is able to be used internationally through your financial institution, though (make sure there are not account restrictions).