J.K. Rowling has revealed the locations of four of the eleven wizarding schools around the world, one of which is in the United States. According to a (very short) page at Pottermore, it’s called Ilvermorny and is pronounced “Ill – ver – morn – ee.”
It’s located in the northeastern United States. I personally know of a few Michigan-based Potter fans who are thrilled at the possibility that it might be located in the Great Lake State.
Other schools include one in Brazil, Castelobruxo (Cass-tell-o-broo-shoo), another in Africa, Uagadou (Wag-a-doo), and the Japanese Mahoutokoro (Mah-hoot-o-koh-ro), an “ancient school” which “has the smallest student body of the eleven great wizarding schools and takes students from the age of seven (although they do not board until they are eleven).”