Just to put a few more facts/observations in play after reading some of the comments on this thread. (a long read I know but hopefully enjoyable to those that do get through it)
AA on US Battleships (and every other battleship) was pathetic early in the war. Most just did not fully understand the threat from aerial bombs. There were exceptions. In the mid-war period US aviator Billy Mitchell sank a WWI surrendered German BB in an airpower demonstration for US brass with a large aerial bomb. The Navy Brass was so upset after having claimed it would be impossible to sink the BB from the air they literally pulled stings to have him court marshaled for it because they deemed he used to large a bomb!
Also note that RN Swordfish literally made of wood and cloth powered by a hamster wheel put the deadly rudder strike on the brand new Bismark not to mention what they did earlier in the war at the Italian port of Toranto (which Admiral Yamato used as the basis for the later Pearl Harbor attack). The fact that the then modern Bismark could not defeat a few RN Swordfish makes the point. Early war AA was woefully inadequate for the threat.
It was not until later in the war that the older US battle fleets were equipped with massive AA batteries. Event the Iowa initial AA designs and configurations were nowhere near what they would be come in the later days of the war. The addition of the any of the older US BBs would just have been more target practice for the highly trained and capable Japanese pilots that sank POW and Repulse. FYI a British carrier was scheduled to go with them for air cover but was run aground and tuned back for repairs. The BB’s went anyway. A costly mistake.
Approaching an Iowa class BB in a plane late ’44 or ’45 was just a just another means of killing your self. Depending on the exact ship they had either 19 or 20 quad mount 40mm Boffers AA (each capable of ~ 140 rds/min, ~ 65 20mm Orklan stations and numerous .50 cal. Not to mention the ten 5” turrets that were capable of being fire controlled in unison to take out any thing in the sky. That is what made the secondary battery so effective in the AA role.
As for a single bomb taking out a BB, yes the Arizona was hit in a forward magazine and exploded but she was actually hit by several bombs that were in large part defeated by armor. One actually bounced of a turret before the fatal blow was struck. The bombs used were actually an adaptation of 14” armor piercing battleship shells specially designed for the Pearl Harbor attack.
The older battleships did not have good enough fire control to consistently hit anything at the longer ranges their main batteries could shoot thus they would try and engage at (relatively) closer ranges. At closer ranges deck armor becomes less important as the shells coming in are not the deadly plunging fire. They tend to hit the sides hence heavy side armor belts and turret armor. Even their relatively week deck armor could bounce a shell coming in at such low angles. Thus the older BB’s were exceptional venerable to aerial attack as their designers did not perceive and design for the threat.
I would argue that the more modern BB’s such as the Yamato and Musashi (sp?) and Iowas would be near impossible to take out with a single bomb. It actually took a total of 27 bombs and torpedoes to sink the Yamato over a period of several hours, (the break out was 17 bombs and 10 torpedoes). Her sister ship who suffered the same fate earlier in the war took similar punishment before she went down. The compartmentalization and damage control of the later ships was much better then the earlier designs.
The designers of the Iowa class estimated it would take 6 near simultaneous evenly spaced torpedo hits along one side of the Iowa class to produce a 90% chance of sinking (capsizing) her. That is with out immediate damage control and counter flooding ect. that would certainly have been employed. The design teams actually altered the design and layout of the engine rooms to make them smaller overall spaces to mitigate the potential threat from a torp damage flooding an engine space(s). A single torpedo would have been more of a nuisance (provided it did not
