It's part a personality issue and an experience issue. My sister makes a 100 mile/160 km trip on a regular basis. Her cat cried and carried on the first two times but finally learned that it was no big deal. Her cat is a little high-strung so it took him a while. to completely settle in but now he's OK with the trip.

Another friend had her cat with her in the car from when he was a kitten and he genuinely enjoyed riding in the car - any car. One time in my car while we were waiting at a traffic light he started hissing while looking out the side window. There was a dog in an adjacent car.