Bretton Woods agreement at the end of WW II, made the US Dollar the world reserve currency, before it was the Britis Pound I beleive

Like the other user commented, it's basically the world financial system. Since nations trade with each other, they need stability in their currencies and traditionally there is always a global currency that dominates all others that nations can all use. This currency is usually backed by something, either gold, or oil, etc.

After Bretton Woods the US Dollar became king. Then after Nixon cut us off the gold standard, they tied the US dollar's value to oil, so that no nation could trade oil unless it was in US dollars. This enforced the entire world using the US dollar, and it also gave us the privilege of being able to just print up money like a bank and run up debts to pay for everything. Henry Kissinger also set up NAFTA under Nixon so that China would produce all of our stuff, and we would buy it from them with our debt dollars. So the entire economy system globally that we have been living under has been this Petro-dollar dominance system where we facilitate all the debts like a bank, and China produces all of our goods which we import using those dollars.

THAT is the system that is coming to an end. China and other nations are bypassing the US dollar to trade oil. The dollar is losing its status in the world. They have been working on a new financial system under the G20 meetings, etc for a while but we don't know what goes on in those meetings. There are likely conflicting opinions about the new financial system. It seems there may even be a Western financial system and an Eastern financial system separate from each other. But this is why we keep hearing about "The Great Reset." I have been hearing about this since at least 2015 under the name "Global Currency Reset" so this has been a plan long in the making.

But regardless, the fact that we can not longer sail along on our king dollar means we have to knuckle down and actually start producing exports again. Now does it make sense why Trump has been working so hard to bring manufacturing back? He knows that the dollar is dead, and he wants to make America competitive on the global trade stage. Most Americans have no idea how fucked we are if we don't start producing and manufacturing again. We'd have a useless currency, and nothing of value to offer for trade. Biden comes from the camp of those who would like for us to just be fucked over when the dollar dies and for America to become plundered just as the USSR was when it collapsed in the 90's.

All of this information I have gathered through a lot of reading. Particularly Jim Rickards. He wrote a lot of great books on this subject. He even discussed how China has been growing influentially in the IMF. The IMF (International Monetary Fund) already deal with international currencies using something called the SDR. But they are very favorable toward China in recent years.