Back in 1971, the USA printed and spent far more paper money than it could cover by gold. Few years later, French demanded redemption of its paper-dollar holdings in gold. But the USA rejected as it actually didn't have enough gold for the dollars it had already printed and spent all over the world, thus committing an act of bankruptcy.
So the USA went to the Saudis and cut a deal-OPEC denominate all sales of oil in US Dollars. From that point, every nation that needed to buy oil had to firstly hold us dollars, which meant that they exchanged their goods and services for dollars, which the Americans just printed.
The Americans brought their oil literally for free by printing those dollars. The ultimate free lunch for the Americans at the expense of the rest of the world.
However, the scam began to unravel when Saddam Hussein started selling Iraq's oil directly for EURO, abrogating the cozy arrangement the Americans had with OPEC, Thus Saddam had to be stopped.....HOW?
But Hugo Chavez (Venezuela President) also started selling Venezuelan oil for currencies other than dollars, so there were a number of attempts on his life and "regime change", traceable right back to the CIA. The PetroDollar cat was out of the bag.
USA concocted up a pretext to wage war (drama of twin tower blast) and invade Iraq and the first thing the Americans did was to revert sales of oil back to dollars. The currency crisis was averted for the moment.
IRAN President, Ahmedinejad, watching all of this, decided to kick The Great Satan in the goolies and do the same thing-SELL OIL FOR EVERY CURRENCY EXCEPT US DOLLARS.
The shell game is coming to an end for the Americans. As the nations of the world find that they can buy oil for their own currencies instead of holding paper US Dollars, more OPEC nations will abandon the Dollars.
That will be the end of the American Empire, the end of funding for the US military and the destruction of the US economy.
The Great SCAM is coming to an end and there's not a lot that the USA can do about it except start another WORLD WAR!