I think you mean soon enough every country will have their own Cryptocurrency , therefore they will have to buy and sell their own cryptocurrencies .
I have no idea why you mean that we won't be able to reach it , the cryptocurrencies are made for the people and it is controlled by the people therefore I do think it will be rather easy for someone to reach it if that's what you mean.
It will be just like fist if there are like separate cryptocurrencies for separate counties.
So there is no point.
It's some kind of consensus, maintained by network. You won't reach it physically, that means any kind of physical violence is useless. This is similar to that you can not destroy religion or language by using nuclear weapon, even if you kill everyone that uses them
And this is very important for the value of countries (coins) on this cryptostar, if any government can control a coin, then it will worth no more than the worth of that government
Currently bitcoin can not be regarded as safe on this cryptostar, since a few mining pools control more than 51% of the network hash rate. However, maybe future development will make some coin extremely resistent from external control