Will Repair – despite Japan’s being the first nation attacked by nuclear weapons, USA’s The Beast from 290,000 Fathoms was also a giant beast released by atopmic testing that attacked cities, and he came out first by a year.
I don’t think there’s much doubt that, at least in the first few flicks, Godzilla/Gohjira was atom,ic weaponry personified. The fiolm came out less than a year after the Fukuryu Maru incident, where Japnese fishermen were irradiated by fallout from the Castle Bravo -bomb test. The fish caught by them had, amazingly enough, been sold and distributed throughout Japan, so that no Japanese could be unaware of the incident – there were wholesale destructions of fish caught about that time because no one was sure of whicvh fish was safe. I’ve seen films of this.
Consider also that, in contrast to those other giant greatures, Godzilla was easily bigger and more destructive. TBF20KF was dwarfed by manhattan. Gojira towered over Tokyo.
Other Japanese monsters, like the aforementioned H-Men, also recall the Fukuryu Maru.
But after the initial run, I don’t think you can explain it as atomic bomb reaction. The monster took on a life of their own.
I do suspect that Japan’s obsession with robots owes itself to a Japanese technophilia. They seem to embrace high tech more readily than the West did. Even when robots were embraced in robot-friendly flicks like Forbidden Planet, Tobor the Great, The Invisible Boy, and the Outer Limits episode “I, Robot” from the 1960s, there’s unmistakeably a sense that, although we can trust these robots, it’s only because we’ve been careful about them, and we still have tobe wary. Whereas Japan’s Astro-Boy was the freakin’ hero of his series.