In a big war like WW2 and in a secondary theater, the easiest POD is for the bad guys in the main theater to do better, so this is the POD I would write a TL using. And use some minor secondary POD. So a sample TL, and if you don't like the PODs, then use whatever you prefer. So the POD goes something like:
1) Since it was a naval war in the Pacific, I need the Germans to "a lot" better. Unlike some on the board, I see Hitler as an inexperienced NCO who was easily moved on military maters in early days. So you need to swap around the early Nazi leadership so they make a bit better decisions on naval matters. Basically pick your favorite WW1/WW2 naval officer, and have him join the Nazi much earlier. In most of these, you don't a Nazi win. You get the Nazi inflicting a lot more damage on the UK, so the USA has to help. Now a Nazi win likely works too, but not required.
2) The "suprise" attack was a big deal. Japan needs to deliver the message better/earlier. So for example, have the Japanese diplomat that comes down in the Fall of 1941 already have the verbal instructions of how to deliver the message. Make it a clear short message that is no more than a paragraph and clearly starts with "the empire of japan finds itself in a state of war with the USA.". You can skip this POD, but it makes it lot easier.
3) Now you need the Nazi to perform better. I like naval German POD's, so I will start with there. We have a better officer/leaders. We can't do something like have the Germans with a large RN size navy, but we can do one with a better War Plan. I like the idea of the Germans having naval aviation like WW1. I enjoy some precision weapons, radar, and magnetic mines. I would focus on these items, but you could do anything that greatly harms the RN. I would write the TL where the naval interdiction was much more efficient. Lot of magnetic mines and guide weapons. Heavy losses to the BEF and to lighter ships of the RN. IMO, the UK will make a lot of these losses good by pulling forces from the east. Then have a followup plan to harm the RN. Russia can happen on time.
4) Then we can start the Pacific War on time. Japan does as well or better in the first few months. Lot fewer UK forces in the theater, some less USA. The USA will be force to send more ships (read carriers) to the Atlantic because the UK will have lost a lot more naval assets. Midway and Coral Sea are butterflied away. The USA will have plenty of forces for attacks in 1943, but Japan will have more time to fortify. Say June 1943 is first big USA counter attack. With German doing much better than OTL, say Torch is cancel and Malta falls, the Italians stay in longer. Germany still loses, but a much more exhausted USA accepts a peace offer by Japan.
Or you could fix Japanese codes, maybe compromise USA codes. Say traitor in Magic program. It is a relatively hard TL to write, but no where near impossible.
But I haven't seen much discussion on if Japan won the war.
