No. Declaring major nuclear war would be a complete economic disaster, especially considering that the world uses US t-bonds to trade for stuff (oil including); every country's investments would be completely worthless if confidence in t-bills tanked. And that confidence is tied up in chinese, russian, european, and US assets. So, those big countries can't really go to war with one another in the traditional bang-and-boom way unless they found a place to funnel all of that capital. That would take years and years to complete.
I think little cold wars will become more common, though.
I think so , one angry dictator /. authoritarian leader who wants to send a message to the free world just has to ignite one nuclear warhead for issues to start arising. america would be against whoever ignited the warhead most likely ( unless it's an ally to which we would just wag our collective finger ). but chances our nations in the middle east and potentially china depending on the reason for such a weapon being ignite may side with the " evil " leader. that gets us into a big divide on whether america has the right to tell other nations what to do ...side pile up against each other and we have a situation eerily reminiscent of the crisis that is eerily reminiscent of world war 1 which much bigger ramifications. only difference is nuclear war is serious and if we engaged in nuclear war we can pretty much guarantee the end of humanity .
that's the double edge sword of new technology the fear that the technology can and almost certainly will fall into " evil" hands . I don't feel research should be minimized in order to keep others from finding technology because the fact of the matter is society stays in balance by outpacing terrorist otherwise a terrorist group with superior technology becomes a major threat. I just think in situations such as those it's important to only reveal findings and technological breakthroughs as they occur to hopefully maintain a technological edge...but at the end of the day it's almost impossible to have a 100% contained security rate.