From the UK perspective
Welcome to the Allied cause Biggles...
1. Definately consolidate your navy into fleets of 12. Achieving a mix is perferrable, battleships, crusiers destroyers. Always have 25% of your fleet destroyers (4units) the make up of the rest is up to you however I like to have 1-2 carrier fleets. Im not sure how many carriers the U.S. has but I tend to consolidate them into 2 fleets with Crusier and destroyer support.
2. Groupings should be for battle fleets and hunter killer groups. Battle fleets are your surface ships crusiers battleships, hunter killer groups consist only of subs and destroyers. The hunter killer groups are very effective based out of the Phillipines and can really wreck havok on Japanese shipping, remember he has a lot of convoys going hit him there and he will be forced to build destroyers for defense or more transports, either way you make him adjust and he has to spend IC's to defend his convoys. I dont know the exact compostion of the US fleet but I tend to go with 4 destroyers and the rest crusiers battleships as the groupings.
3. Basing fleets is tricky but it seems you have identified Japan as your prime opponent. Base those hunter killer groups in the Phillipines. Battle fleets you should move to sea zones where the U.S. has beach heads for now, as the U.S. you dont have a massive defense force, are expected to land in europe sometime, and fend of the Japanese. That leaves little pickings for the defense of the states. Your starting fleets can easily handle any amphib assaults. I recommend that you use the Philipines as your primary Pacific base, just look at its location your right there and you know if you build it up the Japanese will have to defend against it or will attack it. At least you will know where they are and in my expirence I have seen a few decisive battle faught in the phillipines.
Fleets are hard when they are new, it sucks because you cant strat redeploy which makes organizing them more of a pain then ground troops, but apply the logic of ground forces to your fleets. Battleships= tanks, crusiers= mech inf, destroyers= inf. The nice thing you get here is subs, and for the price you get maximum bang for the buck, there tough can fight surface fleets (not realistic but a reality) and hit convoys. If you have the UK as an ally the two of you should be able to rule the seas, just remember those fleets are your homeland defense to start in 36, unless you build units thats all you have to defend the U.S. and you know how MP is anything can happen.
Odin