The only chance that we can have a global currency for this world is the internet based currency as there will be no control from any country based on blockchain.
FIAT can done it as there will be an issue on whose country will be the creator of it.
And its called bitcoin. We are soon to be recognize around the world and for sure motr countries will agree on this. Its hard to have a one global currency because every country have their own belief and the power to create their own. This market cant be control by any government, so i also believe that in order for us to have a global currency is must be base on internet.