I would be interested to know what you are thinking of specifically here please.
As per "War in the Pacific, Strategy and Command: The First Two Years"
The US was being more realistic in pre-war planning as to what could be achieved in the first years of the war. I dont know about Britain, but the US had been working on Pacific War contingency plans since the early 1900's and the Philippines were a major concern. There was even a plan in case of a war against Britain and one for a war against Britain and Japan at the same time.
The Philippines were expected to have to hold on for a time estimated at three to four months before being relieved. WW1 and the Washington Conference of 1921—22 changed this.
The Treaty of Versailles, ending WW1, allowed Japan to keep the German islands they had occupied during the war(Truk, etc.). These islands laid across communication/supply lines to the Philippines. President Wilson objected to them keeping the islands, however secret agreements had been made with Japan that put this into the treaty.
The Washington Conference of 1921—22 in that agreement the United States agreed to no further fortifying of its bases in the Philippines, Guam, the Aleutians, and other islands west of Hawaii. "With that loss, wrote Capt. Dudley W. Knox, went all chances of defending the Philippines and providing a military sanction for American policy."
After these events there developed two camps of thought on the the Philippines the "can defend" and "cannot defend". With the "can defend" also being called the "emotional response". The "can defend" camp had many defenders including Major General Leonard Wood. They argued that Manila and the bays could be turned into a fortress that could hold out until relieved.
The "cannot defend" camp pointed out that even if a Manila Fortress could hold out, the relieving force would have to fight it's way through Japanese held territory only to arrive with low ammo and low fuel and be expected to hold over 7,000 islands in the Philippines. (18th Infantry Division, Malaya)
The US military saw Europe as the first priority and the protection of Britain as being more important than the protection of Britain's concerns. In the Pacific this meant that the Japanese would have the initiative at first. The US military settled on a Panama, Hawaii, Alaska line in order to defend the west coast of US. Then there would be years of fighting to take islands in order to establish supply and communication lines for the advance westward.
It was no easy decision to not try and save those people. And many felt that not trying "would damage the prestige of the United States in the eyes of the world, would have a "disintegrating and demoralizing effect upon our people," and could end only in national dishonor." On Dec.8 we could have mustered all carriers and available forces for a fight toward the Philippines, which would have played into the hands of the Japanese "Kantai Kessen".(As they tried at Midway).
Prewar strategy, I believe the US had a more realistic military view of the situation than Britain. Britain was asking them to defend territory further west than what the US were admitting it could defend. Britain's wanting to hold at all cost is a example of English resolve and determination. Of course Britain's concern may have been more political. The US had told the Philippines that they could have their independence by 1946. Britain may have realized that if they lost what they held, that even when they took them back they would never be theirs again.
