The problem is production capacity. The US has gutted the lower-value parts of its supply chains, closed refineries and foundries left and right, and is thoroughly unequipped to even produce cheap weapons at the rate required to support a war.

The number of airplanes built in the US during WWII is greater than all the airplanes NOT in that category. Obviously we can't maintain that level of industry during peacetime, but we've fallen so far below that level and are so low on weapons that if another major war starts we won't even be able to rapidly scale up.