China would be split into four to six parts - Manchukuo in the northeast, a Republic of China- Nanjing with a seaport but control over most of the central country, direct control along the area on the central-eastern coast, a Guanxi puppet in the South, a Greater Mongolia in the central north, and a puppet Xinjiang/Turkungkuo in the west. Japan will need to industrialize China to take full advantage of her resources amd would probably still try to get French Indochina, the Dutch East Indies, and Burma. But with China out of the fight look for several hundred thousand Japanese soldiers to be freed up and the infrastructure to be improved. Oddly enough Japan was also starting to assimilate some of her conquered populations by war's end, especially in Korea and Taiwan. Given until the modern day there might be a sizable number of people in the modern successor states who see themselves as Japanese and loyal members of the "Dragon Empire" (sounds silly but Japan had dreams to unite much of their WWII realm under the "Dragon Throne" and possibly move the capital to the mainland in the late 19th century). Japan will also be very brutal in its pacification tactics - the pen is only mightier than the sword if the works produced live to see publication, so expect a lot of direct censorship too.
If the Japanese won the Chinese War in 1939-1940, and they didn't suffer from an american embargo, they will still be require to pay for the oil and the US imports and if the USA enter the war in Europe in 1942, the cost of this oil will increase severals times or the exports to Japan will be severely restricted.
If the Pacific War is not provoked by the Japanese, they will still need hundreds of thousands soldiers on anti-partisan duties, raping and killing without pity.
Somewhere in 1945-1946, the IJA and its chinese allies will be crushed under the wheels and the tracks of the Soviet Red Army when the Chinese Red Army will unleash a giant partisan war behind the frontlines.
The "puppets" armies will massively deserted and turned their coats against their former masters. If chinese soldiers had no problems to desert from nationalist to communist forces, they will have no problem to left their genocidal, xenophobic, colonial "allies"...
And the USA will not supported the Japanese in name of the "Cold War", the USA after the Marshall Mission in China in 1946 stopped to support the KMT, their wartime allies, and established an embargo on China.