Still, they wanted to send a strong signal by doing that. Seized goods can be auctioned off unless it's something illegal like drugs. The Malaysian government used the steamrollers as symbolism of what they think of the industry. Personal opinion, of course.
My understanding was the equipment was destroyed based on a court order, so it could very well have just been the opinion of a single judge. Given the (super effective

) Chinese ban on mining, if the Malaysian government had wanted to ban mining outright then I'm sure they would have done so.
Let's say that's the direction the US takes, who could follow them? The UK is the obvious culprit. Maybe they get France on board and Germany.
Who's to say it doesn't go the other way? The US bans mining, and some European countries see an opportunity. They incentivize miners to move there on the provision that they set up near new and developing renewable projects, subsidizing the development of such projects by buying excess energy which would otherwise be wasted during periods of low demand, acting as a demand response system, and paying taxes on the bitcoin they mine.