The US outproduced the axis towards the end of the war but it was a real mess for the first few years while industries retooled and the government broke through obstacles like the aluminum cartel. It was only after Pearl Harbor and the formation of the War Production Board in 1942 that manufacturing really picked up because everyone felt the existential threat and organized against it.
The US can’t make cheap artillery shells because we don’t have much artillery manufacturing. Our armies just don’t use much artillery. We use mostly guided munitions dropped from planes and rockets fired from the ground, whereas Russian doctrine has always focused on artillery.