This is an extremely aggressive approach - the scenario is that the government considers it a threat to national security, which presumes that modifying national laws isn't a problem. You'd be able to detain developers from other countries with extradition agreements, and maybe a few others if you want to risk angering those countries. That'd probably be enough.

A lot of the discussion in the linked post is about specific ways that countries could take down bitcoin, but my main point is that if a majority of large countries wanted to take it down, they have a large variety of tools they could use to do so. Building a lot of hash capability is probably low on the list. The tech is built and run by people, and countries have a lot of ways of exerting power on people, should they consider it important.

Like, the US was arranging coups across central and south america so that bananas would be cheap, I don't think it's too far-fetched to think that violence is a tool they'd reach for to take down bitcoin if needed.