Bitcoin is already kinda an international currency. But i doubt that you can use it everywhere and anywhere. You can only use it to nations that accept it.
it's not limited by nation but limited by whether the shop is accepting bitcoin or not,i think every countries that having online shop there must be atleast one or more shop that accepting bitcoin as their alternative payment method and it's mean bitcoin can be used everywhere as long it's accepted
Bitcoin getting accepted only in few shops in entire country doesn't makes it an international currency, it can be treated as an international currency only if it is widely used and accepted.
No mate, your explanation is only limited to buying stuffs in online shops, there are many ways we can spend our bitcoins including remittance, so IMO it is already considered as an international currency as we transact worldwide in just a matter of minutes, bitcoin connects us and that makes it an international currency.