From a review by Nathaniel Philbrick of Amerigo: The Man Who Gave His Name to America.
It was in 1507, with the publication of a large cut-out map suitable for creating a do-it-yourself globe, that Vespucci’s first name, if not Vespucci himself, achieved lasting renown. On this map, published in the intellectual backwater of St. Dié in Lorraine, the designation “America” (the feminine of Amerigo) was chosen for the portion of the hemisphere where Vespucci claimed to have landed during his second voyage. In 1538, the noted mapmaker Mercator, apparently referring to the earlier map from St. Dié, chose to use the name America to mark not just the southern but also the northern portion of the continent. The rest, as they say, is history. “The tradition was secure,” Fernández-Armesto writes, “the decision irreversible.” And so, because of Mercator and assorted others, more than 350 million of us now call ourselves Americans.