I think an important thing to keep in mind too is that a war started with Japan does not necessarily bring you into the war with Hitler. The Tripartite Pact only required its participants to declare war if the member nation was attacked. For example, Russia did not attack Germany last June, Germany attacked Russia. Japan was not obligated by treaty to declare war on Russia and chose not to do so. If Japan attacks the U.S., Germany was under no obligation to declare war on the U.S. Had Hitler decided to take the same path as Japan and not declare war, then FDR would still have been in a bind to get Congress to declare war on Germany. The isolationist in power are still strong enough to swat that one down and it is the reason why the “Infamy” speech is very careful not to use any word that would link Japan to the Axis or Germany, but emphasis just Japan.
agreed, plus one additional fact. japan tried for a couple years, and especially in 1941 to get Britain and the US to join with them in an anti-communist anti Soviet alliance as a way of being a partner and getting the embargo dropped. Britain especially didnt like the soviets, but didnt really trust the Japanese enough to bite.
then, Japan did in fact attack Russia, which only further isolated Japan since by then the allies had swallowed hard and began treating Stalin as an ally.