Something no one else ever realized? So was the U.S. However, it was hard to use the danger of massed Nazi bombing of the American heartland as a motivator. Ditto the threat of summary execution of shirkers. The idea of political officers producing a constant stream of propaganda was also problematic. Nor was there much of any way to paint the Nazi's as an existential threat after 1943 when it became obvious their defeat was a matter of time. Nor do any of these effect training and doctrine, which was the root cause of German combat excellence. Given the number of Soviet and German prisoners I suspect that "determination" was remarkably localized. Nor did such "determination" do much for the Japanese other than result in more Japanese deaths. So how much faster did British or US troops lose their determination to continue fighting beyond a point Soviets and Germans fought? Do you have examples? Yes, so did old French doctrine..."the morale is to the physical as three to one" remember? Yes, indeed there do appear to be national differences, but it is in the ability to fight effectively, not necessarily the will to win.