In 1969, dashed center lines down the road would have been white not yellow. MUTCD introduced all yellow striping in late 1971 and between then and 1975, the roads would be repainted. Texas had white lines up until around the middle of 1973, but the film was made after the conversion to MUTCD '71 hence yellow striping on the roads in the area.
Throughout the film, Captain Tanner's unmarked blue Dodge Polara is shown to have full-size factory hubcaps. When he is crashed into by the local sheriff trying to "76" the hi-jacked patrol car, Tanner jumps out and the car now has typical police dog dish hubcaps.
During the first chicken eating scene, the chicken bucket is with LouJean. In the next scene inside the car, Slide asks for something and LouJean pulls something (WetNap?) from the bucket and gives it to him. The next scene has the bucket between Slide and Clovis. Time between shots doesn't allow for this because the background song, When my Blue Moon Turns to Gold Again, is playing uninterrupted.
When the helicopter with Lou Jean's father lands at the stadium, although he is seen leaving the helicopter in the close shots on the ground, in the wide shot of it landing, he is not there. Instead, a cameraman is visible in the father's seat, holding a 35mm movie camera, shooting the father's POV footage of the landing.
The "Texas" of this film is a figment of the filmmakers'
imagination. The trip from just outside Houston to Sugar Land takes two days, and Sugar Land is a few miles from the Mexican border. In fact, Sugar Land is a municipality southwest of Houston, not much more than an hour from anywhere in the Houston metro area. And Houston is on the Texas Gulf Coast, two days' drive from the border.
While the Border Patrol's purpose is indeed to protect the United States against illegal entry and not vice-versa, they are still a law enforcement agency that can be called upon to assist other state or federal agencies (as depicted in the film) to prevent wanted felons fleeing the United States jurisdiction during a pursuit. This has happened numerous times in reality and as such they are completely justified in firing at Clovis's car during their attempted escape.