Continuity mistake: During the bikers destroying the Chevy Bel Air, the front headlights are damaged. Some cuts later, the front headlights get destroyed again.
Continuity mistake: The weather changes several times during the bikers destroying the Chevy Bel Air.
Continuity mistake: After Roop drives the police car through the trailer, Charlie in the passenger seat leans back and you see a neck injury. Look at Roop and you notice he is wearing a black jacket, but then only shorts as he reports the incident on the radio.
Continuity mistake: In the kitchen scene early in the movie as Max is leaving to meet Goose, the camera briefly zooms in on his infant son in the floor playing near his clothing/equipment. The child is playing with his service revolver! When the camera pulls back to take in the full room again, there's no sign of the gun. (00:14:43)
Continuity mistake: When the first car crashes at the start the bonnet is hanging off, one of the policeman pulls it off and it lands on the ground upside down, when the car pulls away the bonnet is now the right way up.
Other mistake: When Jessie realises that her baby is missing, she runs out into the yard, stops and does a slow 360 turn before looking forward again. She then hears the Toecutter's voice, looks to her right and sees all the knightriders, including one holding her baby. So somehow in that slow 360 turn she did previously, she somehow managed not to see 15 knightriders standing close to her.
Continuity mistake: As the cop car slides after missing the running felon, the car is shown hitting the sign post, smashing a blue light, then the city names are seen, then the sliding car is hitting the sign post again, and again smashing the blue light.
Chosen answer: It was nuclear war. Tectonic plate movement could make ports dry and flood others. None of the movies ever goes into great detail about the apocalypse.
Grumpy Scot