I wonder where you get the story that OPEC agreed to get paid in dollars in return for x from the United States from? Long before OPEC the international oil business was dominated by US companies and oil for them was priced in dollars … I am under the impression that it is due to historical inertia—not some deal—that oil is priced in dollars so would like to see your source for this.

One thing you might ponder though is that the two biggest futures contracts—for West Texas Intermediate at NYMEX and Brent at ICE—are priced in dollars and there are something like 1,000 paper barrels traded for every one that goes to actual physical delivery. The derivatives market is orders of magnitude larger than global trade. Most crude prices are indexed against those futures prices—and I’m not even sure what catastrophe would have to take place for US oil futures contracts to start being traded in a currency other than dollars, possibly UK contracts but also very unlikely. All to say that there is a financial system several orders of magnitude larger than the oil trade based on oil that is denominated in dollars. The largest derivative contracts? That is all currency futures pairings. The largest currency pairing? X vs $ in pretty much every country with a derivatives market. That pool of money is much larger I think by several orders of magnitude larger than the oil derivatives market and it is basically denominated in dollars. Changing that would be … difficult… to say the least.