My understanding of international finance is far from comprehensive, but if the concern is the instability of the US economy as a basis for global trade I can see the reason for that concern. The 2008 Financial Crisis was largely the product of policies employed by US banks but had major effects around the world. We also have China to consider, obviously bent on economic domination and predicted to overtake the US as the world's largest economy within a decade. The article above also speaks of benefits to developing nations, giving them access to a more level playing field to aid in their own economic growth. On the downside, I'm reading that a global currency would hamper the ability of countries to use monetary policy to regulate their own economies. Global monetary policy changes could have the effect of benefiting some national economies at the expense of others. It appears there is some consensus worldwide that we are not ready for such a system.