Actually, most of those vessels were not sunk in that particular exercise. In addition, our battle groups in war time and exercises and on patrol are not all bunched up like that either. Many of the vessels are miles and miles apart.
And with todays NBC capabilities, we would be able to clean them off and keep fighting.
Hitting a battle group at sea is not an easy task...the oceans are large and the ability to detect, track, target and then launch on and reacquire once the warhead re-enters is not something any other country can really do at this point.
And China would be foolish to open that can of worms. They do have a relative few nuclear missiles capable of hitting our shores...and they would do great damage if they got through the AEGIS BMD and the Land-based BMD.
But what China would get in return would be absolute annihilation.