During the Battle of the Bulge, the German Luftwaffe launched a massive surprise air raid targeting US warplanes still on the ground in Belgium. They destroyed 465 American aircraft, and lost 277 of their own in the battle. Two weeks later, a German pilot held POW by the Americans pointed at row after row of brand new fighter planes sent in to replace the losses, and said, "This is why we are losing the war." The 465 aircraft lost by the Allies constituted a minor hiccup in our operational plans, while the 277 the Germans lost constituted a major loss that could not easily be replaced.
The 8th Air Force had been bombing Germany back into the stone age since 1942. The Royal Air Force had been doing the same thing for far longer. Germany's industrial capabilities were in ruins, while America's "Arsenal of Democracy" was untouched by bombers, and was churning out weapons at a rate never seen before or since in all of human history. We cranked out P-51s and B-17s like soda cans, and churned out Essex class carriers like they were Model T Fords.
The Germans built 18,000 Panzer tanks, 6,000 Panther tanks and 1800 Tigers, for a total of 25,000 tanks. The United States built 50,000 Shermans and the Soviets built 84,000 T-34 tanks.
I'm not saying this was the only reason the Allies beat the Germans, but the huge disparity in weapons production was definitely a major contributing factor.