The U.S. had the best weaponry, and superior military-industrial capacity. The Germans, while technically brilliant, tended to over-engineer everything they made. This resulted in too many systems that could break in the field, and not enough replacement parts and equipment.

The MG42 was a great machine gun, but it didn't win the war. Millions carrying the first issue semi-auto rifle (and a darned good one at that) made the difference on the ground. The Me 262 was a fascinating aircraft, but thousands flying in B-17's, B-24's, B-25's, and B-29's won the war in the air. It goes on and on. The German weapons look great on paper, but didn't amount to much in the field, especially after we became involved.

America prevailed for many reasons, and our weaponry is one of them.