The production in the US was due to more than cheap energy, having all sorts of raw materials on hand was also a big help. Another big help was the machine tool industry seeing a war coming and engaging in a large scale program training people to run machine tools. Having managers picked on th basis of competency as opposed to part loyalty was another big help. Finally, given individual workers some incentive didn't hurt.
The downside of the big push for production was an incredible industrial accident rate, IIRC ~120,000 fatalities between December 1941 and May 1944.
One last fallout from WW2 was that American manufacturing developed a lot of ways to cut down on the amount of labor required to produce a given widget.