Both statements aren't true. AF will provide air support overhead during combat ops, and on call in theater every day. It's coordinated through the joint air control centre (might have my acronym ate up) so those JDAMs might be hanging on almost anything in the US or UK inventory, definitely including naval aviation.
The conditions that can close an airfield to modern aircraft are few, and theatre air taskings are flexible enough that if one airfield or one area is under bad weather, planes come from somewhere else -- I had naval air when I was 700 miles from their carrier, and strategic bombers who came from and returned to the states.
Finally, the GPS system has significant redundancy built in, as does the GPS receiver system on the JDAM kit itself. But given completely absent GPS guidance the JDAM has a fallback inertial navigation system. The accuracy is slightly degraded, but stiill better than first shot artillery. A LOT better -- with a lot more terminal effect.
Right now, we have a continuum of arms in the field from small arms, through mortars, to attack helicopters, to fast movers and strategic bombers. So far, the artillery has not been very useful. There are still potential wars we'll need it for (North Korea, China), but in the GWOT it's been extra stuff to haul around and extra bored snuffies to keep entertained in base camps.
In Iraq, the artillery guys have been patrolling like infantry. It's been a hell of a shift for them but they have done it.
Unless we have another large mechanised war, artillery may well wind up going the way of the horse cavalry, dreadnought battleships, Indian scouts, heliograph battalions, and coast artillery. (Hmmm... maybe we should bring the Indian scouts back? "Hello, I am Sanjay and I will be your reconnaissance element leader today." One more menial job outsourced...)
d.o.l.
Criminal Number 18F