I just spotted another goof. When Jessica Walter and James Garner are sitting in a hillside grandstand discussing why they are so mean to each other they're supposedly at the French Grand Prix. However, looking at the track behind them, it appears they're at Spa in Belgium. It sure looks like the La Source Hairpin at the top and the old pits on the left.
shareI would say that you were correct. Plus, if you look at the elevation change on the circuit in the background...that is most definitely Spa-Francorchamps. The (very short) clip of the United States GP looks for sure like Watkins Glen...and the hotel sure looks like the Glen Motor Inn to me!
shareIt was meant to be Watkins Glen; that's what's engraved on Scott's trophy.
shareThe Charade Circuit in Clermont-Ferrand has a very similar final corner to La Source, plus, there is no Eau Rouge in the background when looking at Garner. I dont think it is a goof. Also, the pit buildings resemble thouse of Charade and not Spa.
Here's the overhead shot of La Source from the movie. It doesnt match with the scene mentioned by the OP
http://i287.photobucket.com/albums/ll126/moppenheimer/011.jpg