Government regulation should focus on how electricity is produced, not how electricity is used. If Bitcoin created pollution or dumped toxic chemicals, I would agree with you. But Bitcoin doesn't do either of those things, the power plants do those things.

So save your regulations for the power plants and let the market figure out how to spend the electricity. If you wouldn't be in favor of the government regulating how much money can be spent on beef, or how much money can be spent on TVs, you shouldn't be in favor of the government regulating how much can be spent on Bitcoin's electricity bills.

Even renewable energy has externalities. They're not as bad as burning fossil fuels but we still want to avoid wasting energy on inefficient things.

Which is fair, but the impact is much less.

The bigger issue with GP's comment is that, even if every major country on earth requires PoW systems to use renewable electricity (which won't happen any time soon in the first place) and can't run on the regular mixed grid, then after switching to countries without such laws (until there are none left), the renewable energy will be bought up at the source and the coal and gas plants will continue to supply everyone else. Nothing changes.

We need to change everything else to renewable before this starts to be effective. It would make a much bigger impact if some countries, where users want to use cryptocurrency, make it illegal to use proof-of-work-based goods or currencies (whatever it's classified as). Suddenly a coin with PoS or something else becomes much more popular and we might, perhaps, shift over to a digital coin that is not a climate disaster.