You may have thought you were a muggle all this time but Joanne Rowling revealed that, if you're American, you're not a muggle because what you are is a "No-Maj." That's correct, "No-Maj" is the American Wizarding World's term for people with no magic. Simple enough.
"Muggle," as many know, is the wizarding world's term for non-magic folk and, it turns out, it is just the British wizarding world that uses this term. As for the spells, it is highly unlikely that the spells would change since majority, if not all, spells have Latin roots.
In spite of the popularity of the term "Muggle," it is completely reasonable that J.K. Rowling put on her thinking cap to coin a new word since Newt Scamander is traveling away from home and hearing new words, especially from American Wizards and Witches, would only emphasize the distance to give him and the audience a sense of unfamiliarity.
After all, there are very obvious differences between American and British English and some of them have to do with how the same thing is referred to such as "fall" and "autumn."
Rowling's revelation is no surprise to those who really follow their books, after all, "Harry Potter and the Goblet of Fire" did reveal the existence of Beauxbatons Academy of Magic in Southern France overseen by Headmistress Madame Olympe Maxime and the Durmstrang Institute located north of Sweden or Norway with Igor Karkaroff as Headmaster until he fled upon Lord Voldemort's return. If different cultures are at play, then different languages and terminologies will be used as well.
The first film in the "Fantastic Beasts and Where to Find Them" trilogy is slated for release in November 2016 with Eddie Redmayne playing the dashing magizoologist, Newt Scamander, who also happens to be the author of the Hogwarts textbook for the Care for Magical Creatures class, "Fantastic Beasts and Where to Find Them."