fiat currency does not drop 50% in one month and is not at the mercy of other countries. If US forbids all banks to execute trades in BTC like China did, BTC is dead.
> fiat currency does not drop 50% in one month and is not at the mercy of other countries.
Fiat currency not controlled by major economic powers has been know to do that (and there are a few cases for major powers, too, in conditions like just after losing major wars with other such powers.)
Conversely, if you aren’t a major economic power, a fiat currency that is controlled by one is at the mercy of other countries. (And, even if you are a major power, your currency has some exposure to your relationships with othe countrieds, though “at the mercy of” may be too strong.)
Not all fiat is “the USD from the perspective of the US”.