These days, with our dependency on electricity and the weapons at the disposal of the big belligerents who'd probably be involved in the next world war, I don't think you can really separate war from a disaster that would cripple not only the internet but electrical grids all over the world.  So I think if a global disaster happened that took the form of world war III, bitcoin would be screwed.  If nuclear weapons are ever used again, that EMP that you didn't want introduced into this discussion would most likely happen. 

Even if the grid was hacked and the electric system was knocked out, bitcoin would be essentially useless in the parts of the world that were affected.  At the very least the price would crash if a large fraction of traders couldn't trade anymore.

On the other hand, take a look at what's happening in Venezuela, which really is in crisis.  They're not using crypto on a massive scale.  From what I've seen from reports, citizens are using US dollars as currency.  So I bet that if a huge crisis were to hit a country like the United States, Americans would probably resort to using some other foreign currency that still has value.  As long as a currency is backed by a government, it still has worth.  It doesn't even matter which government it is as long as that gov't is stable and honors its debts.