I'm not sure exactly how "war production" is defined, but I imagine that the war production of the US would not have been nearly as high as the other countries

I'm not sure exactly how "war production" is defined, but I imagine that the war production of the US would not have been nearly as high as the other countries mentioned in 1940 given that the others had already been at war for a year, whereas the US wouldn't enter until 1942.