You are severely underestimating the necessary level of manufacturing "culture", logistics and processes that were lost when we outsourced manufacturing.
For many things, including probably making N95 masks, we can no longer just decide to make them now without reconstructing that entire logistical tail, all the myriad of small manufacturers, and train people with specialized know-how and the years of experience that only exist in the presence of a vibrant and active manufacturing ecosystem.
The reason N95 masks aren't a good example is that there are manufacturers in the US, and were, already. Prestige Ameritech is one, and it could easily have scaled up very quickly, but couldn't afford to do so and then scale back down within a few months (they've been through this). So, they needed someone to guarantee that they'd be able to sell enough to be worth the investment of building out capability. There were a bunch of stories about this company back in the beginning of the pandemic.
All of that can be regained for a price. Remember I'm being supplied with an arbitrary large budget. There are a lot of manufacturing experts in the US working for the likes of GM who still make things here, if I hire half of them away (for a nice pay raise) I can make all the pieces of the puzzle I need.
For many things, including probably making N95 masks, we can no longer just decide to make them now without reconstructing that entire logistical tail, all the myriad of small manufacturers, and train people with specialized know-how and the years of experience that only exist in the presence of a vibrant and active manufacturing ecosystem.