After the Breton Woods agreement, all the world currencies were pegged to the dollar, which was in torn pegged on gold. But in 1974 the US dropped the gold backing and $ became free-floating. The US maintained their currency supremacy by making sure all the Middle East oil producers would only trade in $ & get the US military protection in return.

In 2021 however, China is the major oil importer and that puts a lot of pressure on countries like Saudi Arabia. Russia, a major oil producer, started trading in euros and yuan. Once the oil monopoly evaporates the US dollar is toast.