The license plate on the car has a 1A designation, which signifies Ada County, which is Boise. Pocatello is in Bannock County, which has a designation of 1B.
In Las Vegas, when Carol plays the $1 slot machine, she hits the jackpot after only playing one coin. In reality, max coins must be played in order to hit the entire jackpot.
A stretch of highway with a large distinctive rock formation in the background is seen right before the scene in which Arvilla gives her friends their sunglasses and scarves. Much later in the film, when they are supposedly in another state, the same stretch of road with the unique rock formation (also same trees, etc.) is seen again.
The first time the 1966 Bonneville is seen it gets a cover pulled off and is covered with dust. The next time it is seen the car is spotless and shiny. The cleanup is not seen, nor the charging of battery and fresh tires etc to make it roadworthy for a cross country trek.
During the filling station scene, as Joan Allen walks towards the car the shadow of the boom mic runs across her face.