The government could just pull a classic "we're doing this because terrorism" with the media emphasizing how great it is, and the masses would clap all the same.

The DoD knows if SpaceX can't launch, they straight up will never get their assets into orbit. The ULA backlog is like a decade.

Right here where I live, in the United States.

I never suggested expropriation in general would be widely supported, but when you have the richest man in the world (who has spent the last year making enemies of virtually everyone other than a small cadre of twitter shitposters) manically making decisions while reportedly on a downward spiral drug bender and he suggests taking action that would lead to endangering the lives of astronauts and an overall weakening of America's national security, yeah the government would have had massive popular support for seizing SpaceX.

If you don't think so I think you might be living in a libertarian bubble.

And this isn't just a random expropriation. While I may have to cry myself to sleep at the thought of our once great nation having devolved into a bitchy slap fest by a couple of narcissistic man babies, the fact is that SpaceX probably wouldn't exist today without the US government, so with Musk having a temper tantrum and saying "I'm taking my toys and going home", the US government would have at least somewhat valid national security reasons to take over SpaceX.

Couple that with the fact that Musk is hated, extremely, by many folks out both sides of the political aisle, means that the rule of law concerns about a SpaceX expropriation would largely be ignored.