You guys aren't serious are you?
You guys who think that the Top Gear guys are biased against American cars should refrain from further comments on the show lest you look more foolish than you already have.
Simply put, you don't understand British humor. British and Australian humor is very ascerbic and should not be taken seriously; especially if it is a recurring theme. They know their comments piss people off and that is the point of doing it, because it makes fools of people who don't get it. It's called sarcasm, and anyone who has been the butt of a joke at a live comedy show understands this.
The fact that there are contradictions in their statements reveal their true feelings. Of all the people, Jeremy's statements should be taken least seriously. Richard and James on the other hand are less sarcastic and tend to mean more what they say. Jeremy makes comments purely for their entertainment value; comedy is "to make fun of", and since cars aren't really "comedy material", therefore either the people who make them or the people who drive them are made fun of.
I don't know what else to say, or how else to educate you on "sarcasm". You either get it by now, or you'll never get it. For those of us who "get it" - we simply just understand the underlying message behind sarcasm - we don't take it at face value.
The "makes you more attractive to your sister" is precisely making fun of you guys who don't understand sarcasm. It makes you look "inbred" to people who understand wit. It wouldn't be made against say Germans or British because they have a better sense of humor and therefore internationally don't have a reputation for appearing dull-witted.