It turned out to be a very good thing that the British talked us into doing North Africa first. Had that same force and commander invaded France D-Day could have turned out very different.
Indeed, Hitler was a dumbass who thought he was a military genius. It didn't help that he deeply distrusted the Prussian aristocracy that was the heart of the General Staff. He made so many idiotic decisions that shortened the war.
I read someplace that there was a secret debate in British intelligence whether they should try to assassinate Hitler should the opportunity present itself. The contra position was based on the fact that Hitler was making so many dumb decisions he was giving the Allies material assistance.
The first WW was so costly to the British and French I don’t blame the former for wanting the Russians to feed themselves to the guns as long as possible before Britain would try to take on the German army one more time. I agree, taking on the Germans in North Africa was necessary practice for the later fighting in Europe. I don’t blame the latter for folding up like a cheap card table in the face of the blitzkrieg.
The idea of the “soft underbelly” was a piece of foolishness of Churchill’s that I think dated back to WWI, and didn’t work worth a dang in either war. Gallipoli chewed up loads of British and British colonial subjects, and overall that war led inexorably to the end of the British Empire.
In WWII, the taking of southern Italy was strategic; there were 13 airfields that were needed to fly long range British bombers across to oilfields in Romania that were ultimately needed by the Reich. But after those objectives were taken and the bombing started, the US finally said enough already and put its foot down for the first time.
The Higgins boats were among the things built in mind-boggling quantities, well beyond what the British thought we could accomplish. If the buildup of that capability had not gone as well as it did, the British would have delayed further, to the point that a 1945 landing would have been demanded.
US manufacture of Liberty boats, all manner of military aircraft (cumulatively well in excess of 100,000 airframes), more than 30,000 Sherman tanks, plus all the helmets, rifles, sidearms, knives, and the training of personnel to something in excess of 10 million — and all while fighting the Pacific War on our own — surprised everyone perhaps apart from Americans. :^)