If this is possible, the butterflies of this are pretty amazing.
Well, first catch your rabbit.
PoD: The "Fordyce Affair".
Endicott Fordyce IV was U.S. Undersecretary of State for Asian Affairs. In July 1941, he was approached by his cousin, Schuyler Van Roon III, a VP of J. P. Morgan, Inc. The Dutch government in exile needed to raise money, and proposed to sell a bond issue by underwritten Morgan. The backing for these bonds would be Dutch revenues from their colonies in the East Indies. However, the security of these revenues was doubted by some potential investors, who were concerned by the threat from Japan.
Van Roon had a "clever" way around this problem. He asked his cousin to provide him with a letter stating "unofficially" that the U.S. would defend the Dutch East Indies against Japanese attack. This would reassure the investors, the bond issue would float, Morgan would make a fat fee and Schuyler would get a nice commission.
Fordyce agreed. However... the letter was circulated to a potential investor, whose secretary who was a passionate isolationist. She passed a copy of the letter to the America First Committee. The Committee published the letter in early August, just after the Atlantic Charter had been issued, and just before the renewal of the draft act was to be voted on by Congress.
In the ensuing hooraw, FDR had no choice but to flatly repudiate Fordyce's pledge; it was the only way to preserve Lend-Lease and the draft. FDR's statement also covered the British possessions in Malaya and Borneo.
With U.S. protection lost, the British and Dutch felt they could no long adhere to the U.S.-led oil embargo of Japan. They resumed supplying oil from Java, Sumatra, and Brunei to Japan. Japan then cancelled its plans to attack the U.S. and Britain in the Pacific.
The respite was only temporary. By November, the Fordyce scandal had been forgotten, and the U.S. again lent its support against Japan. Facing a new embargo, Japan went ahead with its attacks in March 1942.
But the delay was catastrophic for Japan. [molto presto] Allied forces were substantially better prepared, and defeated the attacks on Pearl Harbor and Malaya. (The latter was "a close run thing", but the inspired leadership of Field Marshal Slim, who took over on 10 December 1942, was decisive. The Pearl Harbor raid was a debacle, with the Striking Force ambushed and largely destroyed by U.S. carriers.)
Japan still succeeded in occupying the Philippines, but completely failed to secure the oil supplies required for its war effort. (Brunei fell, but with Singapore in Allied hands, Japan couldn't get any oil out.) American Lend-Lease aid reaching China via the Burma Road equipped a million Chinese troops to modern standards, including an armored corps.
In 1943, British and Commonwealth forces advanced through Thailand and Indochina, the Chinese army marched east and south to meet them in south China. Meanwhile, the U.S. scoured the Pacific. With their navy and air force practically immobilized for want of fuel, Japanese resistance was ineffective.
Allied submarines slaughtered Japan's merchant shipping, leaving the forces in China isolated from Japan.
In mid-1944, the U.S. liberated the Philippines, while Chinese and British forces took Formosa (British ships and aircraft, Chinese troops).
Formosa was the last straw. The war had been an almost continuous string of defeats, but Japan had not previously lost any of its pre-war territory (except a few islands in Micronesia). Also, Japanese cities were coming under long range attack. The Imperial Palace was damaged by stray bombs. The militarist clique was completely discredited. In October there was a quiet coup d'etat, with over 250 top militarists arrested and encouraged to perform "honorable suicide". The new government tried to negotiate, but was stonewalled.
The Chinese army attacked north across the Yangtze in October. Chiang's agents had contacted and subverted many of the Manchurians and Koreans in Japanese service; these now surrendered en masse or even attacked the Japanese, resulting in a Chinese "blitz" all the way to Shantung, while an Anglo-American force landed in Korea to support the rebellion there in November.
Finally, in mid-December, the Japanese asked whether (unofficially) the Emperor would be spared, and whether the USSR would be part of the occupation. Churchill, by this time eager to close out the Pacific War before the USSR could get involved, persuaded FDR that these tacit concessions were a cheap price to end the war. On 15 January 1945, Japan announced its surrender to the U.S., Britain, and China.
Thus, when the "Big Three" met at Yalta in February 1945, there was essentially no discussion of Asian issues. The USSR had not fired a shot in the east, and had no basis to claim any voice in the settlement. Stalin tried to insist that Karafuto and the Kurile Islands should be given to the USSR, but these territories were already under U.S. occupation.
[NB: the three month delay of the Pacific War had little effect on the Hitler War. Hitler was pleased when Japan attacked, and as per his promise declared war on the U.S. The Allied advance in Libya had already petered out, in part due to large transfers of troops and planes to the Far East (larger than OTL).
After the Fordyce Affair, Churchill had become worried that Japan could not be deterred from attacking if the embargo was renewed, as FDR was insisting that it should be. The fall of Singapore would be a catastrophe in the war, and devastating to the Empire. He therefore decided that Singapore must be made
impregnable. When Slim reported that Singapore was much weaker than reputed, Churchill sent him a veteran Australian division from the Middle East, an armored brigade, and 150 aircraft.
Churchill was bitterly criticized for these transfers, which apparently made possible Rommel's revival in early 1942, until Japan attacked and the transfers seemed prescient. They did weaken the 8th Army during a critical period, and allowed Rommel to prolong the North African campaign into mid-1943.
The rest of the ETO played out as OTL.]