Only one country in the world issues a currency that is held and recognized in every country in the world. The U.S. dollar has been de facto the world currency since the Bretton Woods accords of 1944.
Having your money accepted for payment in other countries means the U.S. does not have to earn foreign currency abroad or borrow in other currencies.
Other countries try to earn U.S. dollars by selling more than they buy from the rest of the world. When not earning U.S. dollars, countries have to borrow dollars.
Borrowed U.S. dollars have to be repaid in newly earned dollars. Such U.S. dollar-denominated debt is a real constraint on governments the world over.
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