The MG42, the 88s, and the Tiger tanks were the winning weapons for Germany - but the panzerfaust was the killer. I don’t understand why we just didn’t make knockoffs, it wasn’t like Hitler would sue us for patent infringement.
The Panzerfaust was a good weapon but it had a very short range. In the end the Germans copied our Bazooka and called it the Panzerschreck.
Interestingly, the 82nd Airborne captured a large number of them at an ammo dump during Market-Garden and used them for the rest of the war.
Only the Japanese failed to improve their armaments which cost them dearly. The Zero was their only main weapon which was superior to our stuff at the start of the war. But we outclassed the Zero as the war wore on. Japan did develop a jet plane by the end of the war, but I don't know if they used it.