We’ll I believe they can stack in Burma, forcing Japan to engage or take the sea route which may be contested.
Assuming China will be in a strong position like this, which is a very safe assumption, they probably won’t be in Burma.
To survive long term against Japan, China has to sit somewhere in southern Chinese territories (probably Szechwan). That’s the only way they can continually trade with Japan and achieve their NO. Otherwise Japan can sweep in from the north and cut the road, simply by taking Szechwan. In addition, China can’t build in Burma, so any Chinese infantry there would have to be moved there. I know I’ve fixated on this a lot, but I’m saying that even if Japan attacks and pushes into Russia, they will still be a force to be reckoned with to India.
Getting back to your topic -
I’m assuming Moscow will be a focus of the axis. I am pretty much resigned to the fact that they will be pressured to retreat to Moscow with or without the far east holdings.
Absolutely, particularly if Russia is sending resources (mechs/planes) to the East. Germany will basically have free reign to march right up to Moscow. Actually taking Moscow will take a bit longer, but the trip there will be fast.
The question about Spain: Does it “speed” up the allies ability to make Moscow “irrelevant” or is Moscow always “relevant” because the USA cannot win on its own?
Moscow is always relevant. That struggle decides most games, and is important in all of them. And with Spain, it may help the Allies, as you’ve said. It does make actually establishing European landings faster (no need for quite as much naval dominance as in the Channel). However, Germany won’t let you just roll over Western Europe. It will take some resources from Russia, but Germany does not need 100% to take down Russia, if it plays smart. A relatively light infantry force in France enables Germany to repond to the Allies taking Normandy or Southern France. After their initial invasion forces are removed, the Western front will boil down into an war of attrition in that region.
Germany can’t win if America is focusing on it, you’re right. BUT, Germany does take much longer to lose than Japan does. As a land-based nation, Germany can turtle very effectively. Italy will take part as well, having more freedom in the Middle East/Egypt, because America/UK didn’t focus on it before Germany.
In addition, Russia has a third front to consider, as there is a Turkish army steaming in to the Caucasus.
Ultimately Germany won’t win - America will simply sap too much from the East Front.
However it probably won’t boil down to something so decisive as taking Moscow/Berlin. Rather it would probably become Russia bottled up in Moscow, but indestructible. At the same time, Germany will turtle up in West Europe against the Allies. Who would actually win this fight is fairly irrelevant, simply because of how long it will take.