Unfortunately all the countries are interested in not losing control on the monetary supply. Handing over the control of the currency means handing over power.
China pegs its currency to the dollar. Countries that have already given up monetary sovereignty have nothing to lose and a lot to gain from a world currency.
From this interesting thread:
https://bitcointalksearch.org/topic/which-countries-would-gain-or-lose-the-most-from-bitcoin-as-a-world-currency-124474Considering only large economies, Germany, China, and Canada are the top exporters at over 30% of GDP, while the US, Japan, and Brazil are on the bottom. Germany and China have their currencies tied to their biggest trading partners within free trade zones, but Canada floats its currency, even though 84% of its exports go to the US. So it generally appears that where international trade is high, the disadvantages of giving up monetary sovereignty can be outweighed by the advantage of eliminating exchange rate risk, at least within a free trade zone.
Ravin Thambapillai states that the loss of control of monetary policy affects all countries more or less equally. However any country that pegs its currency to another one has already given up monetary sovereignty, so the main downside of a world currency does not exist for these countries. This list includes China, Venezuela, Saudi Arabia, Ecuador, Panama, many Caribbean islands, and many central and west African countries. Smaller countries in the euro zone have also given up monetary sovereignty to a large extent.
