How do you think Europeans reacted to their discovery that there were entire continents that they had known nothing about? How would that knowledge...

Europeans had actually suspected that there was another landmass in the Atlantic.  Some thought that the Garden of Eden was somewhere in the Atlantic, while others thought that the ruins of the lost city of Atlantis was in the ocean somewhere.  When the New World was actually discovered, Christians thought that it was part of the End Times, as it was told in the Bible that everyone should have a chance to hear the Gospel, and now that the last parts of Earth were being discovered, missionaries should go and preach in order to bring about the Thousand Year Reign of Christ.  Merchantmen viewed the New World as an impediment--something to be sailed through on the way to the riches of China.  For centuries Europe's leading nations looked for a Northwestern Passage.  Part of the goal of the Lewis and Clark Expedition was to find this fabled passageway.  No one realized the continent was this large, and not until the mid-nineteenth century did Americans realize that the continent itself was the real source of riches.