The only reason the armored flight deck proved useful against Kamikazes was that these had little penetrating power. Where an enemy made more conventional attacks using heavy bombs the British armoring system proved very vulnerable and actually amplified damage greatly.
After the crippling of the Illustrious in the Mediterrainian the RN issued recommendations that carriers with armored flight decks under bombing attack lower one of their elevators to allow bomb blasts to vent from the hanger bay should the (and likely to be) flight deck be penetrated.
The other problem with the armored flight deck on a carrier the size of British ones was that it limited the size of the air wing. Weight restrictions were severe with that much mass so high in the ship. Metacentric heights were harder to obtain where there was little risk of capsizing in the event of uneven damage to the ship.
The US solution appeared to be much better. The flight deck was made from thin plate or armor plate about 1/2" to 3/4" thick. This was enough to generally set off most bomb's fuzes. The actual surface was then planked over with wood as were many weather decks on ships of the period.
The hanger bay was an open superstructure that allowed plenty of ventilation particularly of gasoline fumes, a big danger on the ship. The hanger deck, or the deck below that, was typically about 3 or 4" thick and constituted the main armored deck of the ship. This was deemed sufficent to stop most bombs from penetrating to the main spaces and magazines particularly when combined with the burster deck of the flight deck.
For the British armored carriers a flight deck penetration could mean the death of the ship. An explosion in the confined hanger bay (the sides are armored too) would cause massive damage there. A longer fuzed bomb once through the flight deck faced no further serious armor to stop it from reaching magazines or machinery spaces.
As I pointed out earlier, Kamikazes represent a special case. They had no ability to penetrate armor as such. Instead, they typically squashed themselves like bugs on a windshield when they struck armored portions of ships. Their danger came from the massive fuel fires they created. Armor generally protected the ship from this danger too.
As such, they represent a poor argument for armored flight decks on carriers.

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