According to these reports, it is believed that the feature could be rolling out internationally as users are claiming that they are seeing the Apple Pay Cash logo in the iOS Messages app. Apple has yet to officially confirm or announce anything, but the logo showing up does indeed suggest that it could be available soon.
So far users in countries like Ireland, Spain, and Brazil are reporting that they are seeing the feature, although presumably your region would also need to support Apple Pay itself for it to work. There have been sightings in countries such as Malaysia as well, although Apple Pay has yet to be expanded to that part of the world.
At the moment it is unclear if peer-to-peer payments are possible across countries, but chances are it won’t, which shouldn’t be surprising as current P2P payment services do not work cross-country either.