It's been my experience that given the same binary, two researchers will probably find two different vulnerabilities. Given the complexity of these vulnerabilities, I see no reason why any other nation-state hacking service would lose their own, custom-developed exploits.

I agree with your comment in general, except for its confidence in U.S. military capability. Though it would be unlikely for a battle to be waged on U.S. soil, other theaters offer plenty of opportunity for a U.S. loss, especially those that diminish traditional U.S. advantages (such as air and information superiority).