I think I see what everyone is saying, now I could be wrong but these are my assumptions that I base this on.
A) Most of the pacific early game fighting is for island dominance, mainly Indies, Borneo, Carolina, and Phillipeans.
B) Japan has the fleet advantage, but there fleet is primarily defensive based (carriers)
C) Japan fleet has a perceived weakness, no DDs to start and half of there boats (carriers) and venerable to subs.
J1: hits islands, etc. Importantly, 2 carriers in Japan SZ or 1 SZ nearby, 1 AC/Cruiser in SZ 37 near Burma, 1 BB in SZ 50 near phillipeans.
US1: purchases, lets go crazy 5 subs 1 trannie.
J2: hits india, etc. Cannot send boats within range of subs, cannot even block the dang things. Buys DDs.
US2: sends 5 subs 1 loaded AC, 1 DD, 2 bombers to SZ46/Solomon. Purchases 2nd AC, another trannie, maybe a bomber, more subs, DDs, whatever with leftover.
J3: cannot go into any of the above listed islands or die. Best case rally at SZ 50 with DD, but that fleet is exposed to bombers, 4 fighters, subs, etc. Plus fleet maybe splintered. Doesnt even want to hit the US fleet to sink the surface vessels because subs can submerge and counter next round with reinforcements.
US3: island grab time!
And as far as blocking destroyers, a sub heavy US build best get some UK can opener planes in the area!
So I would have to agree that using the above concept in theory can give the US the initiative in the pacific and force japan to dance to there tune!
Now to build just subs is dumb, but 5 subs US1 can put a hurtin on japan.