There is always a chance that a fiat currency will crash, if the government/central bank resorts to reckless policies that break public confidence in the value of the currency.The history demonstrated that all the fiat currencies crashed at some point and they are unstable by nature - they are only backed by the government decision to declare it legal and maintain the illusion of value. It is because the inflation always jumps, the purchasing power drops, and at some point this bubble ruins not only the currency's value, but the whole economy.
I gotta say, you really have some great skills in expressing yourself and clearly you read a lot. What you just said really makes sense and is really a possible way to make fiat crash and become devalued. Frightening, yes, but is something that we just cannot escape from and ignore since it really is such an important matter. Even the roman empire has fallen. There is just no guarantee that this will not happen to any country of today. Which is why cryptos are really such a big help as a storage of value just in case this happens.