[imbeau]

First of all, the US didn't win the Second World War -- a coalition of the US, Britain, France, China, and, especially, Russia did.

Secondly, the US's biggest contribution to the war was manufacturing capacity. Period. Sure, some of the things built in America were designed elsewhere, but the US could outproduce everyone by an order of magnitude thanks to abundant natural resources, a large population, and a heavily industrialized manufacturing base. Not being bombed isn't really a factor in that equation.

Also, America produced its share of extraordinary weapons during (and before) the war -- the Thompson submachine gun, the Jeep, the 50 cal machine gun. American submarines were first rate along with aircraft like the P-51. American trucks were the backbone of both the Western and Eastern Allied supply lines.

It's pretty disengenuous to summarize Americas contribution to the war as you have above