I've thought about that statement and disagree to some degree.
US dollars (here) are simply how we price tangible things when we buy or sell. It is a yardstick. It occupies our brains as the touchstone of valuation. Will it always be that way?
Historically, when currencies implode, people begin to store wealth in other things - gold and silver, art, etc.
To access the banking system in this world - for now - you need to convert from crypto to your country currency.
Will the day come crypto stands alone with direct transfer to another's mobile phone? The technology is already there. It is just not widely deployed.
I think we are in a transition phase. It won't be a smooth line.
I don’t disagree that bitcoin can be valued in other “forms of currency” like silver and gold, or copper or bales of cotton. The reality is that bitcoin ties itself to currency. Don’t forget the utility value of currency. It’s hard to move bales of cotton to get a haircut and then get change in bitcoin.
Besides, what is the probability that all currencies will implode at the same time? Unless bitcoin can be held and transacted easily by billions of people before a currency implosion, a person with bitcoin “wealth” has nowhere to transact very easily. In fact, the energy needed to transact might not be available in the place where the currency imploded.