Well. Americans would be the Coen Brothers, Tarantino, Hitchcock was British but dead.
You have Paul T Anderson - definite auteur - who's American. Tim Burton is a yank too.
Brits. I suppose you can feel when a film is Ridley Scott's. Mainly because he uses the same crew all the time. And Ken Loach's films are (ironically) very much in his image.
The bonkers Ken Russell's films are very distinctive too. He's still alive but living hand to mouth, sadly.
Schooly