[Legbreaker]

...and then the war turns nuclear and NOBODY in the right mind will be found anywhere near a potential target...
I'm sure there would be plenty of volunteers in a conventional fight, but once the shit really hits the fan and areas the size of small countries start to glow in the dark, that supply of manpower will dwindle to a trickle. Desertions will be a massive problem and you can bet those who haven't yet been called up will be making it very hard for the military to find them for reactivation.
Besides, when you're talking 40+ year old ships, there will be a need for retraining of crew. This could be condensed down to a third (perhaps less) of peacetime, but it's still a bottleneck to overcome with reactivating ships.

And don't forget that if the US can reactivate ships and crews, there's little stopping the opposition from doing the exact same thing, perhaps even faster if they have less concern about training quality and small issues such as crew safety and comfort.

Even if the ships could be reactivated in 3 months, crewed and put to sea, we have the small issue of canon stating that the last major fleet in being was put on the bottom in mid 1997. That to me says right there that the best of the reactivated ships are absolutely sunk and it's only the ships which were deemed unimportant or too much trouble/expensive that are still sitting in their probably radioactive storage areas post nuke.