There were several Summer Wars between Japan and the USSR. If these had been succesful for Japan it could have got its oil from Siberia and not be vulnarable to the USN if it had occupied China without occupying the Philippines too. Instead the last and largest of these Summer Wars, the Khalkhin Gol incident, ended in a crushing defeat for the Japanese army in Manchuria. So the oil had to come from Sumatra and the US had to be driven out of their colony The Philipinnes and of course the French colonialists in Indo-China were happy to cooperate. And Solarz is quite right about the enormous resources deployed by Japan against China, but he is wrong about IJN being the largest navy in the world. In the Washington Naval Treaty of 1922 the proportions of battleships, cruisers and flattops in tonnage were determined in the proportions USA to UK to Japan as 5 to 5 to 3. The Treaty was abandoned in the late '30's but Japan had not been able to change the proportions significantly.Not a huge fan of the liberal use of counterfactuals in history, but in my opinion the Japanese would not have begun operations against the USSR even if China had rolled over like Vichy France. Of course such an outcome is not realistic, but it serves its purpose in being so extreme because it shows there are other factors influencing Japanese strategic thinking at the time. Prior to the Japanese advance south, the militarists were divided into two broad groups; those wanting to strike northwards, against the USSR, and those with the 'strike south' policy. Chinese resistance had very little practical or theoretical influence in this argument. The greatest role the Sino-Japanese war played was perhaps in fomenting anti-japanese sentiment in the US, and firmly placing out of Japanese reach a diplomatic compromise with the USA.
Continuing with my "but for" scenario, the Pacific war would have concluded with the USSR rolling through Manchuria, and progressing into Japanese held China. After Midway it no longer mattered how much manpower Japan had; US naval dominance ensured the IJA's strategic role would be reduced to simply defending islands.
This of course does not downplay the role of Chinese resistance in military terms, in their struggle to defend their homes from foreign occupiers; but strategically China could not be compared to the USA, USSR or even Britain given it's contributions in North Africa.
Khalkhin Gol is an "unknown war", but you find a lot about it on the internet.