Actually, aside from the aborted Zumwalts, all US destroyers are still equipped with artillery. The new foreign design frigates being brought into service will also retain artillery systems. Also, the Corps is looking to bring in rocket artillery and more missile system of their own to help compensate.
I would point out that if you’re not in a naval or riverine scenario, the Army is probably the better choice to send in the first place.
One or two 155mm or 5-inch.