The Iowa’s are awesome, effective, beautiful museum pieces. But the cost of refitting them with new energy and tech systems is not worth it.
Raytheon has been developing ramjet missiles which are brought up to ramjet operating speed (supersonic) by being fired from cannon.
I would imaging a ramjet missile fired from a 16-inch gun could be made pretty powerful.
https://www.youtube.com/watch?v=0vIPNElDkns