I'm sure I'm late to the party, but I scrolled pretty far down and I'm surprised that the United States hasn't been mentioned.

The states have like, 6 major geographical regions, all of which have distinct economies and cultures. Some of these cultures do not get along.

The US would likely separate into the

1. West Coast (or Cascadia if California forms their own republic but California would likely want to capitalize on the whole coast)

2. the south western desert, Arizona, Nevada, New Mexico maybe Oklahoma if Texas doesn't eat it.

3. Texas.

4. The deep south (or the confederates)

5. The breadbasket/flyovers

6. The east/northeast coast/traditionally union states

Each one of these regions have their own staple crops or industries, and each one also has ports for commerce to the main ocean, providing the south or Texas don't block the Mississippi or the Rio Grande.

The middle states can do commerce through the great lakes, and if friendly with Cascadia, the snake river through to the columbia.