The best case scenario IMHO would have been for the US Army to adopt a modified diesel powered Christie designed M1931. This would have given the US a tank as good as the T34 from the beginning. In mass production by the US these tanks would have been very formidable foes for the Germans. Of course Christie was incredibly difficult to work and the Army wasn't really in the mood to innovate at this time. So the Soviets ended up with a great tank and the US got the M4. This isn't really a "Supertank!" but it would have been super to save a lot of American lives.
Benjamin
Benjamin