Bitcoin can be international but I do not think we are seeing use in every corner of the globe, yet. Some what not wanting bitcoin to replace fiat straight out either, would prefer side by side.
It is possible that bitcoin could be the international currency in the future if every country in the world would accept it as it is. Many people are now engaged and uses bitcoin.And there are some countries that legalizes bitcoin. That is a good start to make bitcoin as the international currency in the future.