Why US submarines mostly stayed in the Pacific

Did the US Navy operate submarines with the Royal Navy in the Atlantic and Mediterranean during the Second World War?

Only to a limited extent: most US submarines stayed in the Pacific, where British and American boats were separated into assigned operating areas.

Only a limited number of US submarines operated with the Royal Navy in the Atlantic and Mediterranean because the US Navy concentrated most of its boats in the Pacific. Putting many submarines into one theatre complicated control and identification. Even in the Pacific, British and American submarines were assigned separate operating areas. That arrangement reduced mutual interference and the danger created by overlapping patrols. Strategic concentration still required careful management of undersea forces.