In her first installment of "History of Magic in North America," Rowling explored American magic prior to the 18th century. In the Harry Potter universe, European and African wizards were aware of North America's existence far before Muggles (read: "No-Majs" in American vernacular) like Christopher Columbus ever laid claim to the continent, visiting with Native American magical communities using broomsticks and Apparition as early as the Middle Ages.
Similar to the relationship between Muggles and wizards in Europe, Native American No-Majs reacted to magical folk within their communities with either reverence or fear. According to Rowling's version of magical history, the Native American legend of skinwalkers — evil witches or wizards who can take the form of any animal at will — is the result of such fear within the community.
A legend grew up around the Native American Animagi, that they had sacrificed close family members to gain their powers of transformation. In fact, the majority of Animagi assumed animal forms to escape persecution or to hunt for the tribe. Such derogatory rumours often originated with No-Maj medicine men, who were sometimes faking magical powers themselves, and fearful of exposure.
In addition to Native wizards' predisposition for these Animagi-abilities, Rowling also notes that these magicians were "particularly gifted in animal and plant magic," creating potions superior to anything coming out of the European wizarding community. Because they did not use wands to channel magical precision, the Natives were not as apt in the realms of Charms and Transfiguration.
Read Rowling's full entry on Pottermore!
