I think Top Gear is different enough that very few people get it. You sort of have to have seen the show a few times to realise that they are gonna ask you little to nothing about you work, social life and so on and just want to know what cars you like. After all is there another chat show that makes its guests drive round in a four door famaily car for a morning as part of their screen time? I think Goldblum, Cruis and Diaz adapted quite well.
I don't just mean Top Gear though. Seems like they feel out of place on stuff like Alan Carr, Jonathan Ross, Graham Norton and the comedy panel shows too. I don't know if it's the humour or what but it can often seem like they don't understand a lot of it's not serious.
I notice the same thing. There are very few American stars who come onto UK shows and "get it". They seem to work on the notion that they're on the show solely to promote something, rather than just enjoying being on the show. That might work on the US circuit, but it tends to fall flat over here.
One thing they need to realise though; nine times out of ten, we, the viewers, don't give a flying fuck what they're over here promoting. We have advert breaks for shit like that. We just want to see Ross, Clarkson, Carr...etc, ask them stupid questions, have a bit of banter, and then get rid of them in time for the next guest/segment.