Buy 8 Subs on US1 and place them in the Pacific. Move all your ships to Hawaii, including aircraft to either retake that SZ or invite Japan to strike again.
The 8 SS counter if Japan strikes those ships in Hawaii, plus aircraft is a big deterrent for any further Japanese Advances towards Hawaii.
From that point just keep leveraging the SS against Jap fleets and putting 2-3 more SS per round in the Pacific. It really puts Japan in a quandry as Japan has to invest in DD which are more expensive than your SS and less offensively capable in order to protect her fleets from 8-10 SS as fodder with the capability of first strikes against non-DD screened fleets. By keeping the SS in Hawaii, it puts a serious threat on ANYTHING Japan wants to mobilize out of SZ6 without keeping an extensive homefleet to protect it. To me, forcing Japan to keep a homefleet, or abandon SZ6 has a significant ability to slow down a Japanese waterballoon effect of leveraging an empty Pacific of Allied ships - which is the real benefit to the J1 attack - the ability to move with impunity and force the expansion of Japanese holdings. Remember, with those SS you can let Japan take those DEI, and you can just convoy them instead of investing resources to reclaim them all.
With the Pacific settled in that fashion, you can start diverting resources to the Atlantic to fortress up Gibraltar and shut Italy down (which really only requires a few surface ships and SS to convoy Italy out of the game). Even the UK can assist with this, as after the threat of Sea Lion passes, the UK can start filtering SS into the Med which allows the US to get the TT rotation going to start landing groundforces in Europe WAY too early for Germany’s tastes.
The long/short of it, is: Use the SS of the US to slow down Japan, use Anzac/India to retake DEI once the tide has swung and then convoy Japan the rest of the way. Do the same to Italy, and now you’ve effectively isolated Germany against the Allied game of IPC attrition.