I don't think nobody building AI is an option, since we can't control what China and Russia do.
I personally am not concerned about that as far as an existential threat goes, because I don't think AI, in itself, poses one; I think it will hit diminishing returns. But of course it is still capable of serious harm when humans misuse it.
The best analogy we have is probably weapons of mass destruction--we have international treaties about them and we don't let just anybody have them. That's the kind of framework I think we need, and it goes beyond "regulation" in the ordinary sense.
Use of such weapons is considered by international treaty to be an act of war; use of AI by, say, China and Russia against our infrastructure should be the subject of a similar international treaty with the understanding that it would have similar consequences.
Domestically, humans who misuse AI to do serious harm could be treated like, say, the people who tried to spread anthrax years back.