So if Britain makes peace with the Nazis in 1940 (we'll assume the same POD that Wiking used in his Three Little Fish timeline where Churchill is killed in October 1939 in the U-boat attack on HMS Nelson), and Hitler still invades the Soviet Union in 1941, how do things play out in the Pacific? I am specifically curious about:
1) Will Japan still attack the United States and United Kingdom if the UK is not distracted fighting Germany? and
2) How quickly can the US and UK defeat Japan if they are not simultaneously fighting Germany? Can Japan be defeated before the 1944 presidential election or is the war going to carry over into 1945 regardless?
I would think the answer to the first question is probably yes. The British are still going to have to worry about Hitler and Mussolini, so its not as though they'll be able to send their whole fleet to the Pacific, and the Japanese probably won't be too worried about the resolve of a United Kingdom that has already caved in against Hitler, so I think they were probably still throw the dice.
I have no idea about the second question. You can only build aircraft carriers so fast, so even without fighting the Nazis, there is going to be a limit to how big the US Navy can get at least through 1943. Would the British be able to send enough ships to the Pacific to measurably speed up the war?
Also, one related question: assuming the British hold a general election sometime in 1940 or 1941, and that Labour comfortably wins that election, what happens with India? Will a Labour government be willing to support Indian independence if Britain is still facing the (very likely) prospects of renewed conflict with Nazi Germany? Or is Indian independence off the table even with a Labour government in power for as long as the Nazi threat continues?