The modern incarnation and centerpiece of the United States Navy are it's carrier strike groups. These large capital ships are impressive, acting as deterrents to any near-peers such as Russia and China from any preemptive attacks or aggressive proxy actions. The problem these ships are extremely costly to operate, and our most recent deployments, it's like fielding a sledgehammer to smash a fly.
Senator McCain has taken notice, calling for a high / low mixed fleet. A smaller carrier could be effectively used for power projection, sea-lane control, close air support (CAS), and counter-terrorism tasks.
While it is understood we would lose some capability going smaller, we could save billions of dollars in operating costs and field smaller tasks force across the globe allowing the United States a presence more readily available.
With budget concerns being highlighted, the Navy must seek a verity of options to meet mission obligations around the globe and verity of threats while keeping within expectations of costs, effectiveness, and vulnerabilities. A Ford Class supercarrier costs in excess of $13 billion dollars. While an America Class would be around double the cost of a modern Aegis Destroyer $3 billion.
Some deployment options would be limited by the United States going to a short take-off and vertical landing (STOVL) carrier simply due to the limited deck and hangar space. With designs capable of hosting up to 20 F-35B Joint Strike Fighters, of course, fixed wing and rotary aircraft wings would be varied depending on the mission.
While most will say the Ford / Nimitz classes outperform any carrier in terms of amount sorties and air wings, they are correct, it cannot be argued we are able to spread risk and project force in more areas with more assets fielded. These smaller ships still carry a considerable blow to any low-moderate threat in the world when paired with their escort fleets. This is not about the replacement of the supercarrier, this is about a change in doctrine and how we field our forces at any given time.