Songs about yellow submarines come to mind.
What the hell are we going to do with this?!?
The mind boggles.
In relation to the decision to surrender China, whilst I'm not certain if my opponent has made the right move, I think I would have done the same.
In favour of the No Surrender; China could have lasted at least two or maybe three more turns, with the Nationalists holding out around Kunming in the mountains. This could have cost Japan further casualties. They would also have had to maintain a blockade around the Communists, who could have launched some counterattacks that may also have cost Japan a casualty or two. Furthermore, surrendering means that the US Entry effect is
halved.
In favour of the Yes Surrender; China now had no production, although the Commonwealth could have lent them one resource to Kunming, there was only one unit that they could actually build with one production (a Cavalry DIV).
Furthermore it probably wouldn't have been long before the Japanese actually physically cut the Burma road connection and thus no resource would have gotten to Kunming anyway. Also whilst the US entry effect of conquest is much better (for the Allies), the problem was that it was likely to happen in two or three turns - and it was probably better to have half the effect now than twice the effect later, when it was too late.
But crucially, the Japanese are now neutral. They can only do combined impulses until they declare war. This makes the Japanese planning and moves for attacking the Western Allies much more lethargic and slow. It really does make it more difficult for Japan. If the Chinese hadn't surrendered, they could have destroyed the Chinese around Kunming but not actually taken the city until they were ready (which I probably would have done, to be honest). You can 'game' this by declaring war on say Free France - but the US entry penalty goes with it, and you don't have long before you have to attack them anyway.
Finally of course, the Japanese reserves and militia have to return to the Reserve pool. Which by now for me in this game, is a LOT of units (screenshot of that to follow later).

"Look at you - you have HORSES! What were you thinking?!?" - Paratrooper David Webster