Have you ever seen some of the pictures of what Germany had built underground, while being bombed day and night? By no means am I glorifying their war effort and the methods they used, but the engineering required was no less amazing than the Russians moving entire factories in the dead of winter and starting them right back up again to build machinery and weapons to fight the advancing German invasion.
Of course, we went from a isolationist nation with virtually no armament production to the salvation of the western world's war machine in less than two years. If that had not happened, we would never have had the automobile factories that dominated the 50-80's or the steel mills and mines that out produced the entire world when we built the greatest interstate highway system in the world.
All while rebuilding Europe and Japan at the same time.