That’s not totally true: you can prevent Japan taking aus, nzel, haw and Alaska and you can also conserve two NOs for USA and at least one for UK (sometimes two if Africa went well). Dutch East Indies and Philippines are there to take for the allies, and they are pretty rich
A wise Japan can see a full KGF from a kilometer and set a quick attack on mainland America. They start with 5 trannies and is not rare they buying other 2 J1, Polar Express or not. Even if the yanks manage hold the invasion, is enough for axis because for the time USA can restart the KGF, Japan tanks and bombers will be near to Moscow. The problem is Japan has enough money to attack both America and Asia at the same time, specially if yanks abandon the Pacific. And Japan is way quicker than USA
You cannot stop them from taking India, an 8 IPC swing. You cannot stop them from getting there 1st NO that they start with, nor can you take away there island NO until late game no matter what. As far as UK’s NO, without the US in the atlantic it is only a matter of time until Egypt falls, or even Gibralter for that matter. For the occupied Japan territory even that is turn 3 at best for the UK to collect on and puts your boats in a bad spot. Even with the US going 100% pacific japan can typically snipe Egypt. As far as the 2 US NOs, you are not getting to Phi until late game if your lucky, and as for your island NO, japan can snipe it from you on J2 if they sacrifice the transports (when you start with 5 you can spare 'em) just to slow you down or to be a punk.
Italy can be taken down to 1 or 0 of her NO’s by turn 3 at the latest in a full on KGF, and Germany can be kept from getting her 3rd NO in a full blown KGF for the entire game nearly. (put 2 UK figs in Kar turn 1, turn 2 start the good ole Kar shuck).
And even in a full blown US pacfic showdown, G/I can defeat R/UK with ease, as Germany ALONE has a higher income and doesn’t have to deal with worrying about stupid can opener crap. Also, Japan starts with more units the the pacific, and has a higher income than the US. So please explain to me how on earth Japan falls against the US in the pacific unless she ignores it and keeps going after Russia.
And lastly, the US only has a handful of things needed to do in order to tip the balance of power in the atlantic. They simply need to liberate Africa, sink the Italian fleet, and reinforce the UK fleet a bit. And with any luck threaten a drop on Italy and/or France, but this is not required. This only takes 2 to 3 turns to have setup, by then the US can and should start to look at Japan. A polar express just brings Japan to the US.