Why American submarines strangled Japan more effectively

Why did the American submarine campaign against Japan succeed where Germany's campaign against Britain failed?

Japan was less prepared for convoys and anti-submarine warfare, had fewer domestic resources, and had to divide one fleet between commerce defence and major battle.

Japan's weak preparation for convoy and anti-submarine warfare contrasted with Britain's long institutional focus on Atlantic supply. Britain possessed more domestic food and industry and could assign specialized escorts because Germany rarely fielded a fleet large enough to demand continuous Atlantic battle-fleet operations. Japan had to protect commerce and prepare for major fleet action in the same ocean with the same limited naval resources. The United States therefore attacked a more exposed maritime economy than Germany faced around the British Isles.