The US printed unbacked fiat all the way back in the Revolutionary war
That was ok to defeat the British I guess
The US has quite the history of fiat:
" Continentals were not backed by any tangible asset; they were supposed to hold their value on the Continental Congress's expectation of future tax revenues, which, given that they were in the midst of a war, created more uncertainty than the new currency could withstand.1
The Revolutionaries continued printing money and ultimately issued more than $200 million in rebel currency. Within five years, continentals suffered significant depreciation and eventually were practically worthless.3 To contribute to the devaluation of the continentals, the British produced enormous quantities of counterfeit bills to sabotage the American economy. Afterward, the colonies held considerable debt from the war."