They are driving across the country and have gotten delayed with one misfortune, after another so they are running out of time. They are trying to make it to a theme park in California.
Sounds like a fun movie: “Wheel of Mis-Fortune”
The other part of the joke is that Clark Griswold keeps wanting to detour to see every worthless roadside attraction along the way (World’s Largest Mud House or something like that), but has no time for the Gateway Arch in St. Louis or the Grand Canyon.
Amusement park mentality. I recall being at Disneyland and it was 100+ degrees and I was jammed in with obnoxious tourist, their screaming kids, all babbling in 10 different languages.
I wanted to run out of there screaming.