Let's say that China is much tougher in the Second Sino Japanese war, maybe a POD where they manage to rebuild their army in 80 German trained divisions like it was the plan, or something else.
The Marco Polo incident happens as usual, but at the battle of Shangai the Japanese are surprised to find a Chinese version of Khalkin Gol when they are soundly beaten back.
Would Japan keep attacking China? If no, what else? Do they invade the USSR? If not, then what?