Does anybody believe that we could have defeated Germany if England had been occupied ?. Can you imagine bringing our troops across the Atlantic ?. Even at that, we would have had to take back England first. THEN, think of a "D-DAY". By that time the French shoreline would be to the point of breaking off under the weight of German troops and Armament.
Let's see; We all know the cost of taking Iwo Jima & Okinawa. 35% casualties. the top brass estimated as high as 1,000,000 would be needed to establish a foothold on the southern island only 300miles away. With the same rate of casualties. that means 350,000 casualties and awhole lot of stars in American windows.
So; bless H.S.T. for his decision. And while we're at it; cheers to the Norwegians who "Drowned" Hitlers Heavy Water. Without that incident, Harry would have had no dicision to make.