Interesting timeline, reminds me of The first thread I read on this website.https://www.alternatehistory.com/forum/threads/the-guns-of-the-tawantinsuya.11479/page-18
Only more likely, no I'm just reading the first post, I can't wait to see how this develops.
The valley of the shadow of death.
World War II starts late and on a more limited scale with Germany mostly focussed on Poland and the USSR, this leads to the Japanese posesing more in the way of supplies and incidentally their biological weapons programs having more time to fully develop...