Actually, Wired magazine pointed out recently that blowing up Washington would probably cause a massive INCREASE in the effectiveness of our military--and because Constitutional succession would come into play very quickly, we would have something resembling a government again, but without the same sort of metaphorical inbreeding. Wiping out DC would thus tend to make the government AND military much more efficient (and hence effective), actually INCREASE the value of our money.
Not a chance. Our military needs supplies to operate and thus a solid form of value must survive a catastrophy. Green ink and cotton paper wouldn't do.