This is what will generally happen in some years time. Some countries has adopt Bitcoin as a means of making payment and I believe the list will keep increasing till the whole world make it an acceptable means of payment.
It was only about time for all countries to eventually adopt Bitcoin like some countries are already doing now. Because when all countries have really analyzed Bitcoin and it has not harmed the country, Bitcoin adoption will continue to increase over time. In addition, several large companies have also accepted Bitcoin for payment so that Bitcoin payment services are currently starting to penetrate more widely.
I see Bitcoin as a general currency that will later be used by the whole world for transaction. This is just a matter of time. 5 years ago, how many people know about Bitcoin? That's to tell us Bitcoin is moving gradually to the point of becoming a universal currency.
In just a few decades Bitcoin would be acceptable transactions around the world since many countries already acknowledge the existence of Bitcoin. But before that to happen, of course it would affect the economic situation of one country as they prefer already the alternative currency which is the Bitcoin. People wouldn't even use fiat if Bitcoin is the first preferred currency which might impact a lot of country to their economic status. But for sure government would take action from it, as I said there's already countries that are open to BTC and still have a stable economic status.