I'm just going to say this in defense of the American version:
1. Top Gear sucked at first. It took the guys a while to develop their on screen personas and it was only successful because it was the only car show on British TV and was on one of the major channels.
2. Top Gear still kinda sucks. Don't get me wrong, I watch it and enjoy it. But as a car show it is little more than a long commercial that lacks any real tests or serious info about the cars, and don't try to suggest that their track times mean anything, that is sort of a misunderstood running joke. The show is sort of a guilty pleasure.
3. The actual guys on Top Gear aren't that funny. It is funny because of clever editing and ridiculous set ups by the producers not because of the simple and mainly scripted jokes that the guys make that serve mainly to stroke the egos of the British.
Because of these things it wouldn't take much for the American version to be just as good, it would just take time, which I am not sure they will get. Although if there is one problem its that the fat guy doesn't seem very likable to me but we will see (Also Tanner Foust isn't actually much of a driver but that probably won't matter, he is likable enough).