A very interesting scenario where Churchill moves England's military might to Canada. I think a good deal of the population would also have gone along to Canada. The u-boat threat was real, but in the end, it was sheer production numbers that filled the Atlantic shipping routes and supplied the North Atlantic fleet with a spectacularly effective anti submarine naval and air force. That probably would have seen Canada, England, and the US merge into 1 super power. With all the resources at hand there was nothing that couldn't have been built. With the Pacific and Atlantic oceans as buffers, they would remain relatively secure. Mexico might have been dragged in as well, to keep the Panama Canal secure.
The Russians kept the pressure up so that Germany was never able to focus everything on one location. The US sent Russia 400, 000 trucks and jeeps. Plus tanks, airplanes, blankets, boots, all kinds of supplies. The Japanese enjoyed great success militarily, capturing a tremendous amount of territory, but they also could not focus all their attention in one place because of the immense areas involved and long supply lines. This allowed the Allies to pick and choose where they struck back in the Pacific front.
The invasion of North Africa would probably have been different if England was not available as a staging point. Africa probably would have worked as a staging point if England had fallen. It just would have taken longer. Not everything the US supplied for the North African invasion was shipped directly from the US to North Africa. 60,000 of the roughly 110,000 American troops came directly from the US. The other 50,000 came from American troops and equipment already in England. The UK forces, over 100,000, were already fighting the Italians and Germans in North Africa.
Even though the axis powers (Germany, Italy and Vichy) had numerical superiority in ships and planes in the Mediterranean, in the end, it was only what the Germans operated that actually counted. With no naval control in the Mediterranean, the Germans had to reinforce their forces by flying them in from Italy. This decreased their ability to adequately keep the German forces supplied. This was another battle zone where sheer numbers eventually outweighed quality. North Africa was a testing ground for future invasions. After the landings American forces failed to understand that holding the high ground first afforded great potential for not getting wiped out, allowing the Germans to beat the Americans by continually taking the high ground first. When the Americans got to Italy, they were well versed in mechanized warfare, but the Germans still had the upper hand in taking the best land positions even though they were constantly retreating.
The developers of the latest tanks and jet aircraft must have been under immense pressure to deliver,
Unlike before the war, during the war, the Germans did not work together, but in small groups, and they were not sharing information with each other. This was due to personal survival strategy. It resulted in a very large number of inventions all going from the drawing board to the battlefield in parallel efforts, most of which worked. Failure was not an option. Once a program got going, it grew large very fast.