I actually went across the USA for 5 weeks, going up one side of the Great Divide (the mountains, for you furriners) and down the other, and the only kind of trouble we ran into that was related to the car was when the guy I was with got altitude sickness and while he was lying on the ground next to the car while I tried to get him to breathe into a paper bag to stop him hyperventilating, two assumed-to-be-local guys walked over to us, saw our license plate which said Maryland, and one looks at the other and sneers - "Maryland - hah! Sea level!" And they walked away without offering to help!