You are partially correct. The bulk of OPEC and the Saudi regime prices in oil, because we protect them and sell them arms. The Petro dollar cannot exist without the US military backing. But it goes much deeper than the Petro dollar. The World Bank and IMF prop up developing countries, and have similar backing. It is all part of the backing of the dollar. Since virtually all commodities and service are priced in dollars, they need dollar loans to put in ports, power plants, railways, etc ... and they have the full backing of the loan from member countries and the defense of the US that nobody will fuck with their new port. So yes, you are right, but it is also much deeper.