The trick is to let them come to you for the first 5-7 rounds. You must keep your planes, as often as possible, in a position to be able to destroy the Americans if they advance (Kwangsi air base is popular). If you must move your planes to finish China, take Calcutta, or land in Australia to prep for the kill, get your planes back into position to threaten a counterattack against an American incursion ASAP.
The Philippines is a fantastic counter-staging point against Caroline, and FIC with a naval base/mIC (and Kwangsi air base) is also quite alright.
If they go to SZ 6, they are going to need to leave some destroyer blocks to trip you up. If they don’t, you can annihilate them if it’s before round 5, probably even round 6. Your air (assuming you haven’t lost a lot for some (bad) reason) plus your initial fleet is enough for at least 60/40 odds in Japan’s favor, and if you’ve been building a few boats here and there, you’ll be fine. German bombers coming from the Atlantic throws a spanner into any American destroyer block machinations, to the point where I almost ask/do this every game as soon as it’s practical.
You can leave SZ 6 relatively undefended. The destroyer block between hawaii/japan goes without saying, and buys you one round every game (unless the US is mobilizing on midway, which is kinda fantastic to see as Japan because then their mobility southward is hamstrung, so now you know exactly what they’re doing and can prepare). The only thing that matters about SZ 6 is that 1: you keep your capital of course, and 2: if the 18+2 far east ruskies stayed east, then having the Americans in Korea with that stack of slavic crap moving in to reinforce them is a real pain.
I often leave 1-3 fighters on Japan, and am building at least one or two boats after J2 in SZ6. Even if you don’t scramble your fighters to defend a boat or two in SZ 6, the fact that you could will force America to invest something into the fight there if they advance. Maybe they over-invest themselves if you’re lucky.
If America moves in juicy targets to SZ (carriers, cruisers) on a combat move, then by all means kamikaze the shit out of them if you can prep yourself for a counterrattack. A decent American player, however, will not do this early on.
By or just after round 7, it’s very hard to speak in generics, but America can, and should, have more than Japan can handle at their disposal. Your hope then is that Germany is winning the war on the other side of the world, and that the dice are on your side because any naval battles won’t be better than 50/50 for you. Mutually assured naval destruction is not so bad in the Pacific for the Axis if Japan’s economic heart is strong enough to bounce back and retake some Money islands and almost match American naval spending. If America comes back for round 2, Japan probably won’t remain standing, but if America has to come back for round 2, the European Axis should have been bought all the time they need. Japan has done well.
A decent American player will never let you attack him with favorable odds on Caroline, especially with some ANZAC planes/boats there to help out on the defense. Best case: You make him pull back to Sydney/Hawaii. It’s very hard to hit US/ANZAC on either of those, since Japanese planes don’t have a good terrestrial landing zone.
At the end of the day, your goal is to hold out as long as you can if America goes near-full or full investment in the Pacific. Every round after the 5th that you force the allies to purchase heavily the Pacific is a small victory in of itself. And hell, with a little bit of diceluck, you can may even be able to go toe to toe with America/ANZAC for quite a while.
If America consistently invests a lot in Europe (which you won’t see often in high levels of play), then it’s Japan’s turn to go ass wild, and ass wild you should go.
