Until the Treaty was abandoned the RN and USN were, in major surface combatants, exactly equal (rather the point of the Treaty actually), with the IJN 60% of their size.
As far as being smaller - at the end of the construction cycle, I was unaware of the fact that the RN commissioned 22 CV, 9 CVL, 10 fast BB, 53 CA/CL, 350 destroyers, 199 DDE, 96 FF, and 247 ocean-going SS. This of course, does not include roughly 250 canceled ships, ~70 ships completed AFTER the war, etc.
I would also have to disagree with this second statement. Undoubtedly the CO of Kirishima would have been vastly happier to have had something a touch larger than Vickers built 14"/45, especially when scoring hits on South Dakota. The CO of PoW at Denmark Strait might just have stopped Bismarck with 16"/45 Mark IV AP shells (with 800 pounds more weight per shell, greater penetration, better range) rather than having to break off after her slugging match (a 16" balanced design would also likely have shed both heavy hull hits, including the luckily defective 15" round that penetrated to the boiler room bulkhead but failed to explode.
KGV (14") and Rodney (light 16") seemed to have managed to stop Bismark pretty comprehensively...