Anime is sort of underrated for how much alternate history it contains

[Strategos' Risk]

Code Geass is another case of an anime with alternate history.

Thank you, I specifically called it out and bolded it in the OP.

Genuine question: Would Akira count as Alternate History?

As per the OP, it is basically retrofuturism at this point, so no. Or retroactive AH, or paleofuture, as per other responses.