> there is nothing that can be done about it, short of a global ban on computers and the internet

This is not true, there are numerous ways to discourage these harmful proof-of-work systems.

This could be done at the mining source, by states taxing this industry extremely heavily or just banning it outright, and at the point of exchange, with states heavily taxing or banning conversion between normal currency to cryptocurrency. A wealth tax (payable in real money) on cryptocurrency holdings would be another option.

If enough economically influential states decided to do this, we should see a massive crash in the price of Bitcoin and similar cryptocurrencies from this, as people realise it's not worth the hassle of dealing with under these increased regulations.