A 16”/50 caliber Mark 7 – United States Naval Gun trumps that 8” popgun, EVERY time!
I doubt the USA has the capability to build a ship that can carry a 16”/50 caliber Mark 7 – United States Naval Gun, but it would be a fun exercise to resurrect the Montana Class BB and update it to modern times! (https://en.wikipedia.org/wiki/Montana-class_battleship#USS_Montana_(BB-67))
Using a current design essentially means a modified Arleigh Burke hull. I don’t know how feasible it would be to make these ships larger to hold more stuff. The big question is whether a longer and perhaps wider Arleigh Burke class DDG can handle much more in the way of advanced weapons and sensors as effectively as a new design can while being more capable of surviving in a combat zone.