Back in 1944, Bretton Woods tried to come up with how the winners would run their economies after the war. The US unconditionally guaranteed that, for anyone not a US citizen or permanent resident, they would exchange a US dollar for approximately 0.88 gm of 24K gold. Bretton Woods declared the US$ to be the World Key Currency.
I have seen the dollar called the World Reserve Currency, and this seems to be the current term, but, strictly speaking, any currency that international banks must keep in reserve is a reserve currency, and these are the US$, the £, the €, the ¥, and the CHF.
The key currency is the default currency for international transactions. Sellers are afraid the buyer might devalue their currency, buyers are afraid the sellers will upvalue their currency. Gold was recognised as guaranteed, but after WWII, there wasn't enough physical gold in the world to support the expanding global trade, but the US$ was a big enough currency with a value permanently fixed at approximately 0.88 gm gold, so it was declared the Key Currency and made international trade much easier than it had been.
Then, in 1971, was the biggest default in world trade ever: The US said they would no longer give any gold for a US$!
The world economy could have collapsed, but it didn't. The US$ remained the key currency, for reasons no one completely understands (except there was no alternative). The Europeans tried to come up with a key currency not controlled by a single country and created the €, but it only caught on for international payments inside the Euro Zone and so never became a key currency: the US$ reigned.
Iraq and Libya said they'd start accepting currencies other than the US$, so the US destroyed both: taught them a lesson they'll not soon forget.
But, while the US had great success forcing regime change in Grenada, Panama, Iraq, Afghanistan, and Libya, and destroyed the economies of Syria, Iran, and Venezuela, and Americans felt no pain in the US, not the slightest inconvenience. But.
After the collapse of the USSR, the US became Global Hegemon. Graham Allison wrote in 2012 that global hegemons almost always fight tooth and nail to retain their hegemony when they see a rising power that might eventually be able to challenge them, and that rising power was the PRC. So the US planned for regime change in the PRC, and breaking the PRC up into a bunch of small, weak nations that could never challenge the US. Predominantly Muslim western PRC would become East Turkestan. Tibet, Hong Kong, and Taiwan would be independent nations.
But then Russia got uppity, and the US decided to get rid of Russia. After all, when General Douglas MacArthur said the US could easily win the war in Korea by nuking the PLA, President Truman, who had ordered the USAF to use the entire US nuclear arsenal on Japan in 1945 instead said, 'The USSR have MAD. You're fired.'
So the US decided that Russia must be dismantled, the Republics that constitute Russia must become independent nations who cannot agree about anything. The US said that the Ukraine was a candidate who would be admitted soon, then denied that they'd ever said that.
When the US put nukes in Turkey in 1962, the USSR put nukes in Cuba and everyone expected WWIII, but JFK called Moscow and said, "I have to run for re-election and you don't, so if you say you gave the US everything we wanted and got nothing in return, we'll give you everything you want." Khrushchev figured, 'What harm can it do?' and then he had to write the two letters.
Those nukes the US removed from Turkey are now in Türkiye, and the US put nukes in some of the former Warsaw Pact countries. Russia were not happy, and made demands in December 2021, demands the US and NATO said Russia had no right to make, and they would not be honoured.
In 2014, the US neocolonialised the Ukraine. They gave money and weapons to a small group of Ukrainians who consider themselves ethnic Germanic, whose grandparents fought with Germany in WWII, and who agree that Hitler had the right idea about Jews, Roma, and Slavs. The US told them that killing Jews is wrong, and not allowed, but killing Slavs was a great, patriotic achievement during WWII and the Ukraine must be cleansed of everything Slavic. This makes the Ukraine a neocolony: the government must do whatever the US say or they will be removed ASAP.
The Ukrainian government seemed to be planning an attack on the Donbass to eradicate every trace of Slavic language and religion in early 2022, so Russia moved to protect all the ethnic Russians in Eastern Ukraine on 24 February. The US was ready and sanctioned Russia: Russia cannot use the US$, and so is completely cut off from all international trade, thereby destroying the Russian economy which consisted of selling oil and gas to the West for US$ and using those US$ to buy everything Russia need from the West. Oops.
Russia said all oil and gas must be bought with Rubles. Then Russia said the PRC can use RMB and India can use rupees. Russia and China and India are now trading with Iran, who are no longer completely cut out of international trade, and they ain't using the US$.
Using the US$ against Grenada, Panama, Iraq, Venezuela, and Iran caused those countries great pain but did nothing to the world economy. No one in the rest of the world felt any pain, only the countries sanctioned.
Using the US$ against Russia does not seem to be working out all that well. The US has high inflation. The US neocolony of Europe has even higher inflation and not enough oil or gas, so the ordinary people have trouble getting around and staying warm and buying food. But the governments are doing well, paid by the US so they don't lack anything. For the European leaders, bought and paid for the by US, they have petrol and fancy foods and heat in winter and A/C in summer. No problems as long as they do whatever the US tell them to do. Good employees all, they are earning their salaries.
But more and more of the world are abandoning the US$, it is now a semi-Key currency. The control over the world that the US had since the collapse of the USSR, and the US$ as the world's Key currency, both seems to be slowly eroding.
So what will the US do?
Will the US figure that no world at all is better than a world without the US as Global Hegemon?
The PRC and Russia are hoping that, if the US do figure that, it will be after the US$ has ceased to be the Key currency, and the US won't have enough money to pay to launch a nuclear attack.