One thing I have always struggled to understand is how a government like the US does away with fiat.
Notes can be 100% backed by a hard currency instead of by government fiat.
Fiat literally means "because I said so"
Furthermore, you could just have coins worth actual money (aka, silver coins).
And the ubiquity of credit cards in modern society means that it is actually possible to completely replace a cash business with a credit card business. you even have a credit card based vending machines