It is a global currency? It is not going to be the currency that every nation uses, and we are going to just have to accept the fact that we can't do much about this. If you keep on insisting about bitcoin becoming the currency used everywhere, and fiat being gone, then you are going to be upset until you die and won't see that. However, it is working in all nations, even in nations that "ban" it, people still use it everywhere in secret.
So it is a global one, since it is in every nation, and it is a currency because you can spend it to get something. That is all we can hope for and it is a great deal, I personally love it, and will continue to consider the best currency, better than USD.
We do have different Nations
We do have different Government
We do have different jurisdiction
We do have different economy
We do have different fiat
There's no way that it could end up on a single point and on talking about Bitcoin to become a global currency.
It is really just too far of for the said criteria and i dont know on why some are really that too optimistic on something which isnt realistic to happen.
They could rather both co-exist and you shouldnt really be thinking this way because its even impossible to happen even in my dreams.