First, a factual question: About how much money was spent on just the Pacific front in WWII?
The debate question is: If Pearl Harbor had convinced the US to back down and let Japan take over the Pacific and duke it out with China, about how much of China would they have been able to take over? How much of it would Mao have been able to take over? Would Mao have continued to fight Japan until they were off Chinese land? Would he have tried to conquer Japan itself? Or would there have been West (Communist) and East (Japanese) China continuing on into modern day?
If Japan had been able to hold Eastern China and Korea, would they have developed into the nation they are today? Or would they have become something more like South Africa?
The only way that the US would abandon the Pacific would be if Hitler had managed to rampage through both Russia (taking Moscow in '41 and the Caucasus area by October '42) and the Middle East (Rommel) while sinking enough tons of shipping to threaten to eliminate Great Britain from the war. By the end of '42 tho it was clear that none of these things were ever going to happen, tho at the beginning of that year it seemed much more touch and go (c.f. that book titled “1942”).
Psychologically I don’t see the US backing down either. And as far as the meat of your post, China was as much a hotbed of partisans as Russia was, if not more; I don’t think the Japanese would have done much better than historically.
According to wiki, the Japanese Army had roughly 51 divisions (involving 1.7 million men) at the start of '42.
According to my spotty memory from books, the IJA committed roughly 8 to 10 divisions to the side ventures in the Solomons, Phillippines, Malaya, Burma.
The Japanese greatly expanded the raw numbers of men in uniform by 1945, but the quality of the late war formations is spotty at best.
Japan was faced with an “unwinnable” war in China (able to wup the regular Chinese Army forces, but unable to properly garrison the areas held full of unrest and guerrilas).
The Second Sino-Japanese War began in 1937, and near the end of '41 Japan still had not won it. The oil embargo was not initiated until August of '41, so lack of oil, while it “forced” Japan to attack the Western Allies, was not what bogged Japan down in China.