1. It takes years to build and bring online a new fab line, and to train its staff.
2. A "shuttered facility", if there are any in the US outside of DUmmies' imagination, will have obsolete equipment to remove and dispose of, will have to be renovated to accommodate the physical infrastructure needed by modern equipment, and then new equipment installed. And, of course, staff will have to be trained.
Either way, it's a task requiring years, not the weeks DUmmies' imagine would be all that is required.