Timelines in Heike's story (especially the intro) are either wrong or there are three timelines and two copies or McMillans.

1. Americans go back in time (timeline 1) and move the siberite to Alaska. This creates timeline 2 in which America becomes a superpower but USSR struggles. Timeline 1 is a normal timeline, USSR doesn't have siberite here.
2. USSR archaeologists find American stuff dated two million years. They learn about alaskite. USSR goes back in time to prevent the Americans from stealing the siberite. They win, which creates timeline 3.
3. In timeline 3, Russians HAVE the siberite and they attack Heike's homeland. Heike uses the American EON (why would America have it in this timeline?) to go back in time AFTER the Americans do (we know that from Joan), which means there should be two McMillans running around, one from timeline 1 and one from timeline 3.

Either that or Heike comes from timeline 1 in which Russians wouldn't have the siberite at all and the story has an error about siberite-powered tanks.

I suggest changing the story so that Heike's backstory doesn't mention siberite.