But doesn’t that also mean that because you share a sea zone with your enemy, you are required to engage them unless you leave it?
Sort of true. Just that you are able to load units before leaving it. So the exception is of no use if you want to land on a territory which you already own.
True… but if Japan’s choices are destroy the american pacific fleet, destroy the joint indian/chinese army, or destroy the russian army- they probably kill american fleet utterly, buying them several turns of dominance in the sea to systematically win asia.
Get more Axis ships into the open waters of the Atlantic to at least stall the Americans. Tighten the noose on England and hope that Japan is threatening the USA enough that they can’t afford tons of units for the Europe half. Italy has always been the weak point to the Axis, hence why we took them out first in the real war.