As far as post-1942 goes, I imagine having superior numbers, reliable radar, better surface fire control, vastly superior damage control, and ULTRA probably gave the USN a decided advantage. Having a massive industrial base and the ability to easily replace losses didn't hurt, either. During the Guadalcanal campaign, the USN lost almost twice as many cruisers and more destroyers than the IJN, along with two aircraft carriers. However, the Japanese had completely lost control of the sea around Guadalcanal by February 1943. The sinking of the battleships
Hiei and
Kirishima within 24 hours of one another were the kind of crippling losses the IJN just couldn't recover from.
I know I've mentioned it before, but anyone seriously interested in the Pacific War needs to read
Shattered Sword. It explains the inner workings of the IJN and the Japanese naval mindset in
way more detail than I could ever hope to do in a single message board post.
