It is true that, currently, AI does not have any physical "host" in which to reside.

However, the missing link in this reasoning is that AI will almost certainly become far more widely deployed in the future than it is today, and worryingly, consumer devices will surely become powerful enough to run capable AI systems locally.

Once the substrate will be there, once an AI escapes containment, we're toast - I can imagine only solution will be to shutdown electronics at global level.