The thing you're missing is there are no incentives for a sovereign nation to give up the ability to mint their own currency and control its supply (monetary policy).

There’s a reason I said “medium-sized country”. The US, EU, and apparently now China wouldn’t be interested because they are world reserve currencies, or aspire to be in China’s case. On the other hand, you could probably make a case to voters for cryptocurrency to replace something utterly dysfunctional like the Argentine peso. Crypto doesn’t really do much for a country with functioning and trustworthy governing institutions, but not every country has that.