It’s not like WWII where you have a majority population that works on the farm or in a factory with their hands, and at home fixing stuff that breaks. That sort of population can be rapidly redeployed. We would need to start from the basics like “how to turn a screwdriver” for a huge portion of the workforce.
When you really start looking into things, nearly everything points back to China at some point. Pharmaceuticals? The APIs or at least important precursors largely originate there - even if they hit a middleman country first. Then you get into basic components and it’s the same story. That part from India or Mexico might not be available without China as a backstop.
It’s not an impossible problem, but it’s a problem that took decades and a generation or two to destroy. It’s far easier and quicker to destroy things than build them.