Factual error: During the St. Louis part, they show the Griswolds crossing the bridge into Missouri and *then* getting lost in what they title "East St. Louis." East St. Louis is actually in Illinois, so they would have encountered it before crossing the bridge. This has apparently been corrected in the video version.
Factual error: After they leave Dodge City, Ellen says they should stay on US-50. US-50 in Kansas is not a 4 lane, divided highway. In the same scene, as Christie Brinkley approaches in her Ferrari, there are mountains visible in the background. There would be no mountains visible anywhere in Kansas.
Factual error: When driving across the bridge entering St Louis, if you look in the rear windows of the car, High Rise buildings are shown. There are no buildings like these in East St Louis. If you're driving from Illinois to St Louis there would be NO buildings in the rear window.