Peter Dinklage's acting was similar to other characters in the show, namely "Jon Snow" or his brother "Jamie". Since the other leads are not from the Unites States, Dinklage provided an organic nature to his persona that allowed him to associate well with the rest of the cast. It cannot be inferred from the on-screen performance for his nationality.
Yes, Peter Dinklage's acting convinced me that he was British. It is a true testament to his skills that I did not know until very recently that he was the only American lead on the popular HBO series "Game of Thrones." His British accent is so convincing that I did a double-take when I heard his real, American accent during an interview.
I was actually shocked to find out that Peter Dinklage is an American. He fits in so perfectly with the rest of the Game of Thrones cast. He is excellent in his role, and all of the actors work together so well. He has obviously mastered his accent since there is no trace of an American accent during the show.
He has an exotic look and mannerisms about him so I was completely unaware that he is not American. It does not really matter though as good acting is just that, good acting. And by exotic look, I did not mean his diminutive stature or aspects that pertain to that.