We have so much stuff that has value regardless of currency. The economy has so much inertia it would take some natural disaster to upend it.
Well it used to be so. But the problem now is a vary large part of our economy is in the financial sector and alot of the stuff they are creating and trading is based on nothing but Unicorn Farts and Fairy Dust. Then they leverage that stuff and invest in even more UFFD. That is why LTCM, Lehman Brothers and Bears Sterns are nothing but dust now. They leveraged their UFFD to buy even more UFFD and suddenly everyone realized UFFD wasn't really worth as much as everyone said it was.
The big reason the dominoes hadn't started falling is because of the Bretton Woods Agreement. If the dollar wasn't the reserve currency of the world well Greece would seem like financial wizards by comparison to the USA.