During a three-day state visit, Chinese President Xi Jinping held friendly talks with Russian President Vladimir Putin in a show of unity, as both countries increasingly seek to position themselves as leaders of what they call a “multipolar world order,” one that challenges U.S.-centric alliances and agreements. Among those agreements is the petrodollar, which has been in place for over 50 years. In case you’re wondering, “petrodollars” are not a real currency. They’re simply dollars being used to trade oil. Early in the 1970s, the U.S. government provided economic aid to Saudi Arabia, its chief oil-producing rival, in exchange for...