Americans did a fine job with the office. Different from the original, it has credibility all its own, it works, and it's already classic. If you don't like either version, it's understandable, but both have earned their status independantly.
As for Top Gear, I love the show, but doubt it would work.
It's not so much that Americans can't get British Humor. They can. The biggest hurdle is understanding that there's often nothing to get, and that they, as the audience should respond naturally to the tone and language rather than trying to find the hidden meaning.
Top Gear won't translate because about 75% of Clarkson's humor is derisive to Americans. American cars, diets, waistlines... It's all fair game for him, and it would all be lost when they try to Americanize it.
That and the fact that praising high-priced superexotics over American rides like the Vette and Viper sounds better with a British Accent.