Serious threats which have completely failed to persuade North Korea et al to stop pursuing nukes. The closest we've actually come to a nuclear exchange was "using serious threats" during the Cuban missile crisis, and the US is currently losing a war nominally to prevent nuclear proliferation to a state that fortunately doesn't actually have the capacity to retaliate except at very short range. You might remember a few other nominally intelligence-lead claims about weapons of mass destruction too not amounting to very much either...

And in this case we're not talking about bombing sites if they appear to be used for uranium enrichment which isn't exactly an everyday need, we're talking about bombing them if they appear to be optimised to contain lots of computers. You don't even have to be an AI sceptic to imagine a policy of threatening to launch missile strikes on Chinese businesses if they build out capacity in a way distant observers don't like might be more likely to result in millions of deaths than the whatever runs on the Chinese business' computers...