Yes, fiat money was controversial at first, with political and legal peril when the US started printing greenbacks during the Civil War.
https://en.wikipedia.org/wiki/United_States_Note#Politics_an...But after the US switched back to specie (thanks to the large silver strikes and government policy which meant silver coins were priced by government fiat, not commodity value) it took nearly a century before the US fully embraced fiat money. It likely helped that the legal issues related to fiat money were resolved in the 1870s, https://en.wikipedia.org/wiki/Legal_Tender_Cases .
I suspect bri3d was thinking of a timescale in the decade or two range, not 100 years.
The Real ID Act of 2005 still isn't in fully in force, having been extended most recently to May 7, 2025. That should give an idea the likely timescale involved.