I really like the narration at the beginning. I think it adds a lot. Honestly though, if you're gonna make & song about Fat Man & Little Boy, the genre I'd go with would be Industrial Metal since that's a genre centered doom & despair. This honestly sounds more like night club music than a recount of the Nagasaki & Hiroshima bombings.
Even then, I still like how you downplayed the music & tried to simulate the sound of an actual nuclear explosion at 2:30.
I'll scout you for the Audio Portal & upvote your song now.
~ Review Request Club.