There's a map in Black Jack Fairground where you can see the six cities which claim to be the new capital of the United States after the destruction of Washington D.C. These cities are Sacramento (California), Cheyenne (Wyoming), San Antonio (Texas), Montgomery (Alabama), Syracuse (New York) and Columbus (Ohio). The fact that Columbus is one of the capital cities is important because it was the city where Robert had to deliver his bomb.
Morse Code during the opening title says: Bleeding KS [or Bleeding Kansas]
Towards the beginning of the episode, Jake and Jimmy go to check on a town resident by the name of Joe. After entering Joe's home, they discover him under a blanket frozen to death. However, the actor playing Joe can clearly be seen moving his eyes left and right.