I think this also is subject to the fact that today the US navy has not entered any area in force on a wartime footing. You can't just go around with your Phala

I think this also is subject to the fact that today the US navy has not entered any area in force on a wartime footing. You can't just go around with your Phalanx armed if there might be anything non-hostile around you today (be it just an oil tanker of your foe - the PR by causing a massive oil spill is horrendous). A phalanx (or probably the 25mm cannons on the newest Arleigh-Burke destroyers) will quickly tear your swarm to pieces.