If I look at the title you made, I think that right now, or in the generation we have today, we are not yet in a situation where fiat loses its value in any country because of cryptocurrency or Bitcoin.
Then again, Bitcoin, or cryptocurrency, was not created to remove the value of any fiat in every country around the world. Instead, it can even contribute to the good economy of a country that will accept good things here. Right now, for me, "Cash is King," but in terms of digital currency, Bitcoin is King, and we know that here in the field of the crypto industry.