Why nuclear artillery would be excessive for an Iowa

Should an Iowa-class battleship use an Atomic Annie-style nuclear round in its main guns?

No; the weapon could be too destructive for the engagement range, making its effects dangerous as well as excessive.

The question pairs an Iowa-class battleship with the nuclear artillery concept associated with Atomic Annie. The idea fails because a weapon can be too powerful for its tactical setting. Naval gunfire must damage the enemy without making its effects unacceptable at the range from which it is fired. The exchange is a compact reminder that maximum explosive power is not the same as a useful weapon.