Actually, the Iowa class battle ships on display like the USS Missouri are capable of being brought into service on short notice.
I doubt they are in a condition to be returned to service quickly.
The engines alone, being water-tube boilers and steam turbines, have not been fired or turned over in decades at this point, and who knows what state they were in when they left service. These ships haven’t moved under their own power in almost 30 years.
You can’t do that to boilers and turbines.