Regarding Top Gear USA, there actually was a show, it was suppose to be an off shoot of the UK show. The hosts were Adam Carolla, Tanner Foust and one other guy whose name I can't remember. The idea was to have a comic, a real race car driver and a more liberal type (the guy how I can't remember).
I do believe one complete pilot was done for NBC, but the timing was really bad. It was towards the end of 2008 IIRC, the economic world was going to hell, car companies were not advertising and the "car" was being blamed for a lot of the worlds ills (everyone was jumping onto the hybrid bandwagon).
I had communicated with the producer about a future skit but the show was getting the axe. I don't think most people here in the USA really realize how big of a production Top Gear UK actually is. It has great direction, great writing and they do seem to spend a crap load on the quality of the production. With the right hosts and the writing and support to match, I do think Top Gear USA would be a hit. It would be very tough to match the boys across the pond for the way they click together though.
Cheers,
George