One reason Ma Duece was so "feared"...
Is that we put them on everything that could physically carry them. Planes, tanks, trucks, halftracks, scout cars, even jeeps (although a .30 was more common on jeeps).
One huge advantage we had during the war was that our industrial base was secure from attack. Another was its sheer size. Although it took nearly two years, when the US was fully ramped up as the "Arsenal of Democracy" only the Soviets came close to matching our production, and then, only in a few areas (like numbers of tanks), but they could do that because of the support they were getting from us.
When you look at the amount of material we send them as aid, you can see that allowed them to use their own resources for other things. When you are getting a lot of your trucks from someone else, that means those factories can make tanks, for example.
The Germans had some fine engineers (although they did suffer from tunnel vision alot), and a very, very capable industry. However, to balance this, they also had the Nazi regime, which often forced their industry down exactly the wrong road at critical times.
When you consider the size of pre war Germany (several of our states are larger), even looking at the amount of area they controlled at the height of their conquests, versus the size, and production capacity of the Allies, the fact that they kept the issue in doubt for so long is amazing.
All else being equal (and it almost never is) bigger bullets tend to work better.