The Japanese could NOT bypass the Philippines.
Unlike those of us dealing with the scenario the Japanese had to deal with reality.
The reality of the era was that the United States had the ability to cut off the Japanese supply lines between the entire Southern Resource Area and the Home Islands from Manila Bay and Clark Field. The U.S. HAD Guam a potential major island base that could easily be brought up to speed (and was, in fact, supposed to be so upgraded) that posed a vital threat to the Japanese League mandate island of Saipan. The United States was, in December of 1941, within weeks of completing a B-17 base on Wake. There was only one potential target for B-17s operating out of Wake, the Japanese bases in the Mandates.
The reality of the era was that, in July of 1940 the United States Congress had approved the largest peacetime naval and aircraft building program the world had ever seen. The United States did not need
EIGHTEEN fleet carriers to intervene in Europe, it also did not need
four Iowa and five Montana class battleships,
twenty seven cruisers and 40 submarines to deal with Europe. There was only one potential enemy that the Vinson-Walsh was aimed at, and they didn't speak German. The Japanese knew that. The Japanese knew that if the waited to oppose the U.S. until the Americans decided that they were ready to fight that the U.S. would crush them like bugs.
The Japanese also knew that they were rapidly, dramatically, going broke. They had a very limited time to construct a defensible perimeter, get the essential resources needed to survive, and be ready to hold against the U.S., If they left the Philippines, Guam, Wake, American Samoa, Johnson Island, etc. in American hands they would never be able to establish a perimeter since the U.S. would hold bases at every choke point across the Central Pacific.
The reality was that the United States had entered WW I because of a telegram. Not because its forces or possessions were attacked. It entered the war because a couple cargo ships were sunk a really stupid telegram from Germany to Mexico. Japan had to figure that reality into the plan.
In planning for war you have to account for threats. Once identified you have to honor them and come up with a way to neutralize them.
The question isn't if Japan could have ignored all the threats posed by the U.S. bases and U.S. building program based on sixty years of hindsight and reading of the Presidential papers of every President since FDR, the personal papers of most significant members of Congress of the era, it is if the Japanese High Command was stupid enough to disregard ALL the threats posed by the U.S.in 1941. They were not (although they were stunningly clueless about their enemy). No military officer would have been.
The Japanes could have bypassed the Phillipines. It seems to me the result of doing so would have been better for them than what happened OTL.
FDR's willingness to do pretty much anything against the Axis except take America to war is so impressive partly because many Americans were disinclined to follow his lead. FDR's political skills included an ability to gauge how far along into the conflict he could bring Americans at a given point in time. I don t believe he would have expected the country to go to war absent Japanes attack on US possessions/forces
In August 1941 Congress voted 203 to 202 to renew Selective Service. A country that closely divided about whether to maintain a sizable army is not a country ready to go to war against Japanese Imperialism. A New York paper ran an editorial titled "Who'll Die for Dong Dang" after Japanes troops attacked French outposts in Tonkin a few months earlier. The writer's answer was that Americans would not. Substitute "Singapore" or "Rangoon" for Dong Dang and the answer from many, many millions of Americans would also have been "not my kid".
A major buildup of US forces in the Phillipines and elsewhere in the Paciifc would have continued, increasing the ability of the US to strike hard at the Japanese. The willingness, of a Congress that came within 1 vote of again reducing the US Army to Ruritanian proportions, to go to war for Dong Dang et al on AUgst 13 1941 was just not there on Dec 6 1941
