Some countries have a sufficient manufacturing base that allows them to spin up mass manufacturing of (for example) masks over a month or two.
You don't need to keep spare capacity for everything, but you need to have local capacity (not necessarily spare) for building custom manufacturing machines and staffing them, so that you can divert it to manufacture arbitrary physical goods if needed. Some countries can do that, most don't - but some of these could and should build that capacity.
You don't need to keep spare capacity for everything, but you need to have local capacity (not necessarily spare) for building custom manufacturing machines and staffing them, so that you can divert it to manufacture arbitrary physical goods if needed. Some countries can do that, most don't - but some of these could and should build that capacity.