World War II without a two-ocean US Navy

How much longer would World War II last if the United States entered without a two-ocean navy?

Perhaps another two and a half to three years, because the United States would first need to build a much larger fleet.

The United States could not immediately execute a global naval war without enough ships for both oceans. The conflict would therefore last roughly two and a half to three years longer. That delay represents the time required to build the missing fleet rather than a change in American industrial potential. Prewar procurement determines the operational tempo available after war begins.