Michael's Earth 5E
Mystery Magic Number: 605,895,995,773.
Lots of old information about the setting is on the 2E site.
This Earth has had 17 tactical nukes launched in a little over 100 years, when 2/3 of cultures don’t know about steel yet.
Aziza’s Plan (see here) pushed the plot on alt timeline 1, and Prism called the shot to force the game to alt timeline 2.