Japan maybe inflicts a few 100 more casualties on U.S. aircrew, but not much else. Unless you also mean to introduce kamikaze a year sooner...
Japan's problems are, as noted, resources, but also organizational. IJN needed a dedicated ASW command, & not just one year sooner. That said, introducing the Mikuras in 1941 (& then actually building more than a couple of dozen
) could have hurt the USN Sub Force efforts against Japan's trade: not enough to alter the outcome, but enough to cost a couple or so subs. (I wouldn't want to try & pick which ones...but I'd dread it being Wahoo or something.)
Japan's problems are, as noted, resources, but also organizational. IJN needed a dedicated ASW command, & not just one year sooner. That said, introducing the Mikuras in 1941 (& then actually building more than a couple of dozen