I think fiat money value differ in every state since economic stability and government protocol differs as well including cultural values which is also another factor that affects economy. In my country fiat money does not always fails but like cryptocurrency it does increases and sometimes decreases too. However, the flactuation rate is not as high as bitcoin.
It might slightly differ per country, but the general picture is still the same. It's nothing more than a system that's based on debt and continuous creation of more fiat that's overflowing the economy with long term consequences.
The fluctuations of fiat currencies might not be as severe when you compare them in a direct face to face manner, but if you look further, fiat currencies experience crazy volatility as well, but no one talks about it.
I remember when I was buying stuff from the US (not crypto related) €1 was worth almost $1.40 per conversion, where last year, when purchasing Bitcoin, €1 bought me significantly less than $1.10 worth for a short while.
If these aren't insane fluctuations, then I don't know what is. Bitcoin goes through insane fluctuations in a quick fashion, while fiat does it over longer periods of time, which means that fundamentally, there is no real difference.
These fluctuations of less than 30% over a time span of a few years are nothing when compared with Bitcoin volatility where you can see that much in a matter of days a few dozen times within a single year (not even speaking about other cryptocurrencies). Honestly, I can't even imagine how you can call such fluctuations insane. In my view, they are nothing out of the ordinary, while insane is on order of thousands %% like price first grows 10 times, then falls 3 times all within a few months.