Tip of the iceberg. They showed The Avengers and The Prisoner in their original format. Other than that, I can't think of much (except on BBC, obviously.)
We export our culture. Our shows and movies are shown world-wide. But TPTB assume we don't want to be contaminated by having to watch any other country's exports. And it tends to be a self-fulfilling prophecy. They never get shown here so most people never develop a taste for them. Their loss.
ETA: Here you go. I wouldn't really count reality shows. Most country have their own versions of Dancing with the Stars. People like seeing local people compete. But we also don't import scripted TV.
List of American television series based on British television series - Wikipedia, the free encyclopedia
That opens up another whole can of worms, best left alone, so I won't make the comment that comes to mind.