Everyone can generate electricity with solar panels or wind turbines, etc. Even if there wasn't a central government at all, bitcoin miners would still have resources to defend their operations.

If things deteriorate to the point where people were forced to self-sufficiently generate their own electricity, one of the last things they'd waste that power on is bitcoin mining.

Furthermore, you need semiconductors to run a bitcoin miner, which are so complicated to manufacture that, in the absence of a government, either manufacturing would stop or the manufacturer would become a government.

Sure. They can. Assuming that they're not reliant on the power grid to back them up when their solar or wind isn't generating so well.

But, even assuming ideal self-sufficient power generation, their Bitcoin are useless unless the rest of the blockchain participants confirm them.

Which requires an interconnected system of networks. An Internet, one could say.

And guess what? the infrastructure to run a national computer network, never mind an international one, also relies on the rule of law and the authority of nation states to provide continuous service.