Apple Pay Cash reportedly starts rolling out globally6
One possible feature of Apple Pay Cash that has not been tested (since there was no reason to until now) is the ability to send money to a recipient in another country. It might be best to wait for Apple to make a statement before attempting to send some cash over the U.S. border, since you might end up paying a high fee for such a transaction.
Apple Pay Cash launched in the U.S. early last December when iOS 11.2 was disseminated. The update was pushed out earlier than expected since it contained a fix to exterminate a bug that was causing iPhone models to crash.