I think it's safer, faster, and the country can save on the cost of printing their own country's fiat currency. we all know that the costs a country has to spend on printing their currency are very expensive, and cryptocurrency is the solution...
Exactly. This is a hypothetical scenario that if all the countries converge to the crypto, it will bring much economic prosperity but that would indirectly mean letting go their existing wealth which no country would.
Realistically thinking, you will understand that we will never see it. The governments will never refuse from their national currencies to convert to the cryptocurrencies. Meanwhile, they can stop to ban crypto.