There are many countries in the world that claim to be the first "true" Republic. Whether they are right or not, the concept of Republic is a very old one. In fact, different civilizations have adopted different types of republican systems for centuries. In all honesty, many of these civilization adopted a limited form of the republican system but still contributed to the ideology that most countries adopt today in one form or another, the representation of all the people.
The Romans and the Vikings were probably the first non-natives to visit the Americas. Although not a well known fact, Roman coins were found in Canada, Florida and South America. Whether Romans did visit out of exploration or due to a shipwreck is unknown as no records remain of their visit. However, we do have records of Vikings' explorations of Northern Canada. The Viking did name the new continent but they also abandoned the New World thus making their exploration more a visit than a discovery. Thus, the naming of the new Continent did not happen until few years after Columbus' arrival to the new world. It took 15 years until another Italian explorer would be responsible for naming the New World.