When Anne and Dan are talking in the kitchen of the California motel suite, the electric clock on the wall is plugged into an outlet but the second hand does not move.
When the family arrives in Saint Louis for the first time, a US flag can be seen flying. However, this flag has 50 stars and in 1953 there were only 48 states.
The action of the movie is supposed to occur in the summer of 1953. In one scene a Greyhound Scenicruiser bus is shown leaving a bus terminal. The Scenicruiser did not enter production until 1954.
The shirt Robbie is embroidering has an Interstate Highway system logo for I-66 on it; it should be a US Route logo for US 66. I-66 wouldn't exist for many years, and wasn't anywhere near where they went.
The movie is set in 1953, yet when Anne (Renee) is seen walking through town just before her husband shows up at her apartment in L.A. There is a car parked on the side of the road with a modern (late 90's early 2000's) New Mexico License Plate.
In the scene where Anne goes into her sister's house to get George, she is standing in the kitchen with a small picture to her left. There is a reflection of a crew member in it.