The Flying Belgian
Third Tall
Which ban? The 1924 immigration act? Not gonna try and defend that but it seemed very broad and Japan one of the countries impacted seemed almost incidental considering it seemed to target restricting Italian other European immigration more directly. The militarisation of Japan commenced much earlier, signified by them defeating Russia in 1905. It'd be a stretch to say that American immigration restrictions was a significant or even noteworthy factor behind the militarisation of Japan and the attack on Pearl Harbour that brought the US into World War 2, though admittedly I'm not familiar on Showa Nationalism and will need to read up on that.
It is recorded that Japan declared a day of mourning and humiliation when the law was passed. I think there was also a commission in the US post-WWII that pinpointed the passing of that act as a contributing factor. I mistyped about the militarisation of Japan, because that had already occurred - you are quite right.