Don't know how much this has been discussed, but l think with the second map snippet it's now rather obvious.
- "New Pavonya" is a reference to the original name of New Jersey (
Pavonia, New Netherlands)
- The left map snippet starts with "YO", which very likely also spells "Yorke", just like the "Yorke Bay" in the right snippet => New York state
- "Endless Isleland" is a long sliver of land reaching into Yorke Bay from the Northeast => Long Island
Educated guesses:
- "Silver Head Mountains" => Appalachians (maybe Catskills in particular)
- Top-left island on right map snippet => Manhattan?
- "Victory Island" => Staten Island?
- Ravenskill => Catskill?
EDIT: Part 2 of my theory:
The Astonishing is an allegory to DT themselves. The Empire is the music industry based in NYC that creates a mechanized drone of artificial music, lulling in people.
The rebels (aka DT) are from Long/Endless Island who play Forbidden Music.
I'm calling dibs on this theory.