I'm watching The Hitcher again, and I know that the film is supposed to be a little stylised and require some suspension of disbelief, but I wonder at how John is somehow in all the places Jim runs away to, and after watching the film a few times in the past, I wonder if Jim is dead, since all the events of the film happen after he falls asleep at the wheel.
I've never thought about this before (though other people probably have many times), but it makes the film make so much sense if Jim's actually in purgatory the whole time and John's some sort of Devil figure (the devil is portrayed with blond hair and angelic features in multiple media). I'm going by a Judeo-Christian religious interpretation here, since I'm making the perhaps too broad assumption that the writers and directors of this film come from that background. It's American, so I suppose Christianity is the major religious influence.
If the cops are really the infernal (or angelic? Is there a difference?) authorities, then their quest to judge Jim's innocence in the murders decides whether he'll ascend or be send further down into hell. Nash could be either a fellow resident of purgatory or a heavenly figure. (She does say that if she's with him, the police won't dare shoot at him, and then she's shocked when they do. Fucking typical angels.) John's warring desires to make Jim like him and have Jim destroy him also make a lot of sense. The weird scene where no one picks up when the cops call the numbers Jim gives them also make sense, and the cops almost seem to know the calls won't go through.
Jim seems to figure out that John kills everyone that Jim trusts or proves his innocence to. In the middle of the film when the guy at the diner asks Jim what happened to him, Jim firmly replies with a no multiple times, and I felt like Jim wanted to protect him. However, he desperately wants a friend and someone to believe him, so he confides in Nash despite his better judgement because she believes in him and wants to help him.
The gas station blows up with fire reminiscent of the 'fires of hell.' When Jim uses the white pristine hotel shower for the first time after being bloodied and dirty, he reaches his hands out under the water spray with cupped hands like he's receiving a benediction, and when John turns on the television after kidnapping Nash, the broadcast that Jim hears is about the apostle Paul and keeping the faith from a Texas church broadcast. John keeps trying to get Jim to commit murder so that he'll tip the scales and be cast into hell. In that sense, John wins in the end because Jim hijacks a police car and goes off on his own to kill John.
In the end, Jim kills his own perception or incarnation of the devil with a preternatural calm. He knows exactly why John wants him to kill him, and he knows that it's inevitable. The filmmakers originally wanted Jim to kill unconscious John in cold blood instead of in retaliation, which I think would have made for a much more powerful scene and really cinched the film together in a perfect way. Even though John is dead, Jim is now stuck and perhaps a little more like John that he would like. A lot of people have theorised that John saw something in Jim that made him think he would be a good protege and that Jim would take over for John after he was dead. Maybe that means that a little bit of the devil is inside everyone, that evil is a trait of people instead of a supernatural figure.
As the credits roll, we see Jim's silhouette against the sun as he stands smoking a cigarette like he has all the time in the world. Maybe he knows he'll be there for a long long time.