i find this extremely doubtful. I see the point of your statement, but i'm willing to bet 99% of all the already built nuclear devices wouldn't work today. There's no way that they're all stored in such a way that the delicate mechanisms are protected from the environment and oxidization, moisture ingress, insects, heat and cold expansion and contraction.

That a nation could make a new device is arguable, that a nation could make a device that could be delivered without flying planes over another country is less arguable. Even nukes as they stand would only pose significant threats to certain parts of a country (there was a map floating around the web a few days back of areas of the US most susceptible to the - pardon the pun - fallout from a tactical strike.)