No Japanese war with China = no Pacific War at all.
Why would there even BE a war?
The Japanese have no need for oil, they have no significant friction with the U.S., UK, France, or The Netherlands.
The only way a war starts is if someone high in the command structure goes utterly nuts and orders an unprovoked and unsupported attack.
I would agree that without Japan being involved in a war with China the likelihood of a War iin the Pacific is just about ZERO.
Well, this skips over alot of intermediate questions to simply say, no 1937 China war = no Pacific War, for certain.
The two most important intermediate questions are:
a) assuming it is not butterflied away, how does Japan react to the fall of western Europe to Hitler and the obvious opportunity to easily occupy French Indochina (which they did before the oil embargo, not after), if not other European colonies
b) given (a) above, do the western powers embargo Japan?
On the one hand, they have not had years of getting morally outraged over a hot war in China from 1937 to 1940. So they may not react as harshly to Japanese moves to occupy French Indochina.
On the other hand, Japanese occupation of French Indochina in 1940 or 1941 (or threats to the USSR for that matter) could prompt a western oil embargo/asset freeze, for strategic reasons. In occupying French Indochina, Japan would be signalling a possible intention to scavenge other western colonies and generally profit from the distress of Germany's enemies. With the US determined to hold onto its empire, and the US and UK both wanting successful British and Soviet victory over the Nazis, they may well decide to try to restrain Japan with economic weapons.
An embargo on Japan, if it is not negotiated away, puts you right back to the situation for Tokyo of submitting to western demands or plunging to capture the resources of the DEI, and therefore needing to take Singapore and Manila etc.
---there's plenty of other intermediate questions to consider between 1937 and 1940 in terms of possible knock-ons from there being no China war getting started:
1) With less need to support Chinese resistance from 37-39, do the Soviets up the ante in Spain?
2) What is Japan doing in the meantime- what forces is it investing in? Do they patch up relations with the anti-Hitler coalition or do they continue a policy of greater friendliness with Germany and Italy (dating to the anti-comintern pact? HMaybe they would even send some volunteers to Spain alongside the Italians and Germans (I doubt it, but you never know, especially if there's any trade opportunity involved.) How do they balance Army and Navy modernization?
3) Is the Japanese Kwangtung army still having summer battles with the Soviets from 1937-1939? Maybe they do because the Japanese want to enforce a certain claim on the Manchukuo-Mongolia border. But maybe they don't, their probing actions may have been related to testing Soviet reactions and strength in the context of the China war (ie, how much of a threat do we face up north, and therefore how many Kwangtung divisions can we afford to move south of the Great Wall.
4) What is China doing? I personally doubt it would start a war with Japan in 1937 to 1940, but Chiang had been forced to call off his offensive against the communists as early as 1936 to form a United Front.