Reserve currency doesn’t last forever.
Much of the US position as World Hegemon, World Dictator, and King of the Unipolar World rests on the dollar being the world’s reserve currency or fiat currency. In fact, one of the reasons Iraq was attacked was because Saddam was threatening to go off the dollar and instead transact his oil sales in another currency. Iran already does so. Soon after regime change, one of the first things the US imperialists did was to reverse Saddam’s decision to go off the dollar and put all of Iraq’s oil sales back on the dollar. So much for the humanitarian mission of the sickening, Nazi like war of aggression known as the Iraq War (I prefer to call The War on the Iraqi People).
No fiat currency lasts forever, as you can see above. America can bully, bluster and threaten away, but some day, the sun will set on the dollar as world fiat currency.