What do most buy US1, US2……
W/US I like to place on the Pacific side early, because if Japan delays attack (J3) you can still move your fleet away from port and get into position at Queensland to strike the DEI on US3/US4 when you get a chance (plus you still have the option to move through Panama to go Europe if Japan attacks J2).
Because I only get to place 3 units I like to buy 2 carriers, and a BB for 52 IPCs US1 for the west coast (make a statement). Get the big boats out of the way that can absorb hits and you already have the air to put on the carriers. US2 probably add 3 destroyers for screens and fodder and fighter(s) for allied airbases… and maybe a carrier or couple destroyers for EUS. The first 2 US turns you are building a defensive fleet to withstand a Japanese strike, US3 you start building to go offensive, so subs/air probably. I like a few US subs to trade destroyers w/Japan (economics), and maybe get a chance to convoy some of the DEI until I can take them depending on what Japan does (force them to expose/waist destroyers picking off your cheaper subs).
I have played games where the US and Japan just keep playing cat and mouse w/super fleets and won’t attack each other (very annoying). I have been known to split my US fleet leaving a large carrier/destroyer group to bait Japan into attack as long as I have a counter attack set-up with US subs/destoyers and air power followed up by an Anzac clean-up to finish off wounded Japanese capital ships (can be tricky because Japan could do a hit&run). Its a gamble, but even if you come up a bit short the Japanese can’t replace lost ships and keep the land battle going. Getting Japan to hit you isn’t easy, but they know the clock is ticking… This is normally around the time that Japan is making the final assault on China (or India), so all their air power probably won’t be available (best time to move in?).
US3/4 start piecing together an Atlantic fleet w/UK (Canada) to start a shuck-shuck to Gibraltar. If Japan does a J2 attack, you have the option to move your US1 purchase (2 carriers, and BB) through the Panama canal on US2 (to West Indies) and build on EUS at the same time. US3 all move to Gibraltar…
Building on the west coast US1 just makes more sense to me (unless J1 attack because you may want to go all out Europe) and keeps the US versatile (maybe disguise a Europe campaign).