The petrodollar system creates ongoing global demand for USD to buy oil (20% via Hormuz), letting the US run deficits, borrow at lower rates, and enforce sanctions effectively.
Iran requiring yuan payments chips away at that demand, which could gradually raise US Treasury yields, weaken the dollar, boost inflation/import costs, and reduce geopolitical leverage—per analyses from Investopedia, IMF history, and recent de-dollarization studies. It's not an overnight collapse but an erosion of the "exorbitant privilege."