@ Cruisers
This is where IC-days efficiency and naval force composition come in. CAs are just as vulnerable game-wise to attack as CLs, as they are not designed to soak up damage like BBs can. However, churning out a fleet of CLs is much faster than doing the same with CAs, which means greater production efficiency if you build them in a long series, with multiple parallel builds; which the USA can easily sustain. Naval force composition is the other major reason, as CLs count as screening vessels versus CAs counting as capital ships. When you have more capital ships than screens, your fighting capability drops (AFAIK you can't see it in the combat modifiers, but it's there), and your ships take more hits from enemy fleets. With a 12 capital ship (CV,CVL,BB,BC,CA) to 18 screen (CL,DD) fleet mix, your ships will take less damage and if you happen to have an FC-brigaded group of CLs with a BB/CA heavy fleet in bad weather, can absolutely wipe the floor of even a CV-full fleet as long as you have CVLs.