> Does the US invest in manufacturing like this anymore?
No, but that is different from not investing. Today the US invests more in automation and engineering and less in manual labor.
> if there were a war today would the US be able to produce as much as it did in WW2?
It took several years to ramp up to WW2 level production. We would see the same, a couple years of trouble on the fronts while building industry at home, then when the industry is built up massive production.
Historians (amateur so I'm not sure if they are right) tell me Hitler was ready for WW2 first and Italy begged him to not start the war as their industry wasn't ready. However France and Briton saw the war coming and were building their industry and so waiting might have made things worse.
I wonder how history would be different if Hitler had told France and UK to f** off with the WWI reparations stuff, threatening a war if they tried military action to force payment, but then didn't invade anyone and concentrated on developing their economy and becoming a technological and manufacturing power.
No, but that is different from not investing. Today the US invests more in automation and engineering and less in manual labor.
> if there were a war today would the US be able to produce as much as it did in WW2?
It took several years to ramp up to WW2 level production. We would see the same, a couple years of trouble on the fronts while building industry at home, then when the industry is built up massive production.
Historians (amateur so I'm not sure if they are right) tell me Hitler was ready for WW2 first and Italy begged him to not start the war as their industry wasn't ready. However France and Briton saw the war coming and were building their industry and so waiting might have made things worse.