hi.. can you clarify: are you referring to the country (i.e. the United States of America) or the continent (i.e. variously known as America; the Americas; North & South America; or North, South & Central America...)

I went looking at this antique map dealer, and found this woodcut print from 1553:

http://www.jpmaps.co.uk/map/id.33542

It shows North America identified as "Baccalearum" apparently in reference to early European cod fishing.

This page from the same dealer:

http://www.jpmaps.co.uk/map/id.36710

features a woodcut print from 1546, and refers to"Waldseemuller's map of 1507" as the earliest to name America. Apparently that's kept in the Library of Congress:

http://www.loc.gov/loc/lcib/0309/maps.html