Magellan was the Spanish explorer who discovered South of Chile in 1529.
No South American explorer discovered Australia.To see who really discovered Australia, see the related question below.
The Italian explorer Christopher Columbus discovered the US in 1492. Of course, it wasn't called the USA then. Also, there were already people living there.
Columbus
Henry Hudson discovered the Hudson Bay.
Spanish explorer Vasco Núñez de Balboa discovered the Pacific.
french explorer La Salle discovered the Ohio River around 1682, this explorer also explored the Mississippi River but did not discover it.
Abel Tasman was a dutch explorer that discovered New Zealand.
Christopher Columbus accidentally discovered America for Spain.
Ponce de Leon
Columbus
Erik the Red.