[inglor_cz]

"That is how the world economy used to work, before the petrodollar."

The petrodollar is about 50 years old, and international trade grew IDK, fivefold? in that period. No surprise that the previous patterns don't hold any more. There is a difference between a market of three villages and a market of fifteen villages. If the # of connections between corporations and nations grows quadratically, it becomes infeasible to juggle around dozens of different currencies. The market will trend towards dominance of one.

"Euro is irrelevant outside of Europe."

But Europe is fairly relevant in the world. About 20 per cent of forex reserves worldwide are kept in Euro, it is the only serious, though not peer, competitor to the USD in this regard.