How will Argentina block transactions, will they e.g. buy 60 000 000+ Ethers to control a majority of the decision power on the Ethereum blockchain? This would definitely drive up the price of Ether and even if Argentina had 100 000 000 000+ USD to spare, maybe there are other priorities? Argentina is going to make a digital peso? Haha, maybe they can pay out the ñoquis with them, other people will just keep using stablecoins pegged to the USD as USDC, USDt and DAI. Argentina can see which accounts contain cryptocurrencies, but they cannot see which account belongs to whom, unless you reveal it. As if Argentines are now revealing all their bank accounts. If you have an account that is revealed, you can still use a mixing service as
https://en.m.wikipedia.org/wiki/Tornado_Cash for people to lose track where you send your money to.
They may introduce a digital peso with the constraints they choose, but it does not mean that people will use it. After all, the first popular blockchain, Bitcoin was created with the sole purpose to make central banks and their currencies obsolete or at least to provide an alternative. Governments that think that they can control how cryptocurrencies flow do not really understand what is happening.