When the show spoofed the WWE last year they actually goofed on the wrestling fans for watching a "play" in the ring. They equated wrestling with acting, and, in fact, acting was more desirable by the WWE owner, Vince McMahon. You could tell that the writers had some idea about the subject they were satirizing. No such luck with the NASCAR episode.
I will give the show credit for not taking the easy way out and goofing on the redneck fans ("they took our jobs!") again, instead they made Cartman the bad guy. Cartman spent the whole show lamenting over the fact that he was not "poor and stupid" enough to succeed in NASCAR. If he said that line once, he said it a hundred times.
The entire premise was to show that the drivers are not stupid. Indeed, only Cartman was stupid, and they had a press conference with some star drivers to prove it. Cartman became progressively more racists, stupid, and Southern as the show went on, and that was the funniest part.
Dale Jr was wearing a Bud uniform from three years ago. Danica Patrick got the most air time, and the most lines. I'd say it was a very lazily written episode, and not even Danica getting ran over could save it.