Why the United States could prefer many 16-inch guns

Why might the United States keep the 16-inch gun instead of adopting an 18-inch weapon?

Established infrastructure could produce far more 16-inch guns, trading a little individual shell power for faster and larger fleet output.

An 18-inch gun offers a larger individual hit but demands new manufacturing, handling, and shipbuilding infrastructure. Existing American 16-inch plants could continue producing proven weapons in much greater numbers. The choice is therefore between marginal punch and fleet-scale output rather than a simple ranking of calibres. British 18-inch service would still exert enough competitive pressure to change American and Japanese decisions.