Before the Harry Potter movies were made, author J.K. Rowling set down a big rule that film studios had to follow if they wanted to have her on board, though it was broken a couple of times.
It was strictly enforced enough that when Robin Williams called the director and asked if he could be in Harry Potter to play Hagrid the answer had to be no.
The role instead went to Robbie Coltrane, while Columbus said that Williams also wanted to try for the role of third-year Defence Against the Dark Arts teacher, Remus Lupin, but was again rebuffed in favour of David Thewlis.
Of course, there were several non-British actors in the Harry Potter movies as a decent number of the cast were Irish, including both Dumbledore actors Richard Harris and Michael Gambon.
Still, Rowling's rule was really more concerned with her story about the boy wizard not being turned into an American-dominated tale by movie studios.
With that in mind, there were only two American actors actually cast in the Harry Potter films, though you won't have heard their voices when you watched the movies.
One of them was director Chris Columbus' own daughter Eleanor, who appeared as Susan Bones, a girl who is sorted into Hufflepuff by the Sorting Hat during Harry Potter and the Philosopher's Stone.
She doesn't have a speaking part in the film as Harry (Daniel Radcliffe) is far too preoccupied about his scar hurting and mistakenly thinking the cause is the death-glare he's getting from Severus Snape (Alan Rickman).
While Harry is too engrossed in his own personal drama, Susan Bones gets sorted into Hufflepuff and then it's Ron's (Rupert Grint) turn to don the talking hat.
In a later appearance in Harry Potter and the Deathly Hallows, she was played by Emma Jayne-Corboz.
The other American who appears in the Harry Potter films also shows up in Philosopher's Stone and that's Verne Troyer, who provided the physical acting for Gringotts Bank goblin Griphook.
However, Warwick Davis provided the voice for Griphook and later played the role when the goblin banker returned for the final two films.
One could argue that there are technically three American actors in the Harry Potter films since Zoë Wanamaker was born in New York City, but when she was a child, her father was blacklisted due to his communist views.
He'd been over in England for a play at the time and upon hearing of his blacklisting decided to stay in the UK, meaning his daughter has British citizenship and has spent the vast majority of her life in the UK.Featured Image Credit: Warner Bros.