Japan's entry could pull the United States toward a naval war

Japan's alliance with Britain could divide American opinion in several directions. Isolationists could argue that Britain no longer needed American help, while those expecting a future war with Japan would worry about leaving Britain indebted to Tokyo. Continued British-Japanese cooperation would also give Japan combat experience and access to technology unavailable to a neutral United States. Cutting off Allied supplies is judged unlikely because American industry profited from them and German power remained a concern. Trying to keep American equipment out of Japanese hands would be difficult once it reached a shared war zone. A limited naval commitment could offer operational experience and influence over the peace settlement without requiring an immediate American ground campaign. Such participation is considered plausible in 1941, after a prolonged political argument. British and Japanese claims to be defending freedom could also turn American exceptionalism against continued isolation.