hello...
a one-world currency is highly improbable given the rampant nationalism that still exists in many parts of the world. the European Union is the only functional bloc that has pulled this off and much of that has to do with the unique history of Europe itself.
many countries would consider a currency forced upon them as a violation of sovereignty. just think about Latin America and the nationalism that surrounds soccer, let alone just about any other country in the world.
Ironically, we have had a one-world currency, to an extent as the US dollar was the global reserve currency after the Bretton Woods accord of 1944. It is still the reserve fiat currency today, however this will in all likelihood change soon and the opportunity for a great lesson will arise.
One may also look to China as an up and coming economic power in the world. Much of their success has been based upon controlling their exchange rate to ensure their exports remained cheap.
Even if a global currency was forced upon the entire world, hypothetically speaking, this system would quickly deform into regional trade blocs and regional informal currencies.
It boils down to an issue of
enforcement.
Just my two globally hegemonic cents.
