i think bitcoin is already an international currency because i see that nowadays bitcoin is acceptable in everywhere and bitcoin transaction is very faster than other currency and we can say that bitcoin is already international currency.
I agree with you could see bitcoin users already spread all over the world, almost every country may have bitcoin users, it means bitcoin can be used in all countries, and it proves that bitcoin is an international currency
As mentioned bitcoin from the day of existence had served as a international currency with its transaction taking place crossing borders with the reduced processes and transaction fees. Only thing is that it is not regulated by countries because of decentralized system. Now on experimenting countries have been making plans to regulate within countries. Such move help bitcoin to be announced as international currency.