There is evidence of the Phoenicians in Brazil as far back as the 7th century BC. They even left an inscription saying they had come from Sidon and that commerce had cast them on that "distant shore". The Phoenicians are one of the best known sailing civilizations who were known to have sailed past the tip of Africa. The Greek historian Diodorus even wrote about Phoenicians finding a great island beyond the "Pillars of Hercules" (Straits of Gibraltar). They may have been caught in a storm during the voyage and thrown off course and ended up in America. Or, its possible they may have been intentionally looking for a new place to trade with. Contrary to popular belief, people didn't think the world was flat in ancient times. That was a myth started by Washington Irving in his biography of Christopher Columbus when he erroneously stated that Columbus was trying to convince people the world was round. He was actually just trying to convince them that it was thinner - they already knew it was round. His theory was it was quicker to sail West to go East...but he was wrong, because he underestimated how wide the Earth was...and didn't realize there was another big continent in his way. With that in mind, it could be that the Phoenicians were aware of the possibilities of finding other lands and were purposely looking for a new trading outpost.
But it doesn't end there. The ancient chinese have stories of a land called "Fusang", which is thought to have been the west coast of the Americas, probably around Mexico. And it is perhaps more than just stories too. During the 5th century AD, a group of Buddhist monks sought the paradise of Fusang and eventually found it. According to a Readers Digest book I have called The World's Last Mysteries, they found a cultivated people with "system of writing, but they have no fortresses or walled cities". What is more interesting is the fact that in Mexico, terracotta sculptures of faces that have distinctive Chinese, Phoenecian, and even African facial features have been found. If the people of ancient America had never seen these people, how could they have possibly known what they look like?
And its not necessarily just the stories of Phoenecians and Chinese either. The ancient natives of America also have stories of the "gods" visiting. One example is the story of the Aztec "god" Quetzalcoatl. As the story goes, Quetzalcoatl sailed away on a raft vowing to return some day. Five hundred years later when the Spanish conquistadors arrived, the Aztecs thought this was the return of Quetzalcoatl because they had been expecting "bearded white men dressed in different colors and on their heads round coverings". According to one theory though, the original Quetzalcoatl may have been a viking known as Ullman from the 10th century AD. The theory is supported due to the finding of germanic runes and a rock carving of a bearded figured with what appeared to be Viking ships on a carved cross.
Another curiosity is in the United States at a placed called Mystery Hill in New Hampshire which consists of stone structures that don't match the architecture or style of the natives. It actually appears to be Celtic in origin and archaeologists even found tablets alluding to the Celtic God Bel and the Canaanite God Baal. In addition to that, there are various stone chambers around the New England countryside that appear to be Irish/Celtic in origin and may date to as far back as the 8th century AD.
Here are a few other mysteries (which might be hoaxes or possibly have better explanations):
- In Heavener, OK in 1976, an ancient coin that appeared to be Syrian in origin was found with a depiction of Emperor Nero on it. (It may be possible a modern traveller carrying an ancient coin could have dropped it though)
- In 1968, Manfred Metcalf came across a stone in Georgia that had inscriptions similar to the ancient writing from Crete called Linear A and B.
- A rock outcropping in Colorado that had inscriptions written in Consainne Ogam, an ancient Celtic form of writing.
- A painting found in the Roman city Pompeii that includes a pineapple and a specific species of squash - both native to the Americas.
- Egyptian statuettes were found in Acajutla, Mexico in 1914.
- According to a 1909 article in the Phoenix Gazette, an Egyptian tomb was uncovered in Arizona by the Smithsonian...although the Smithsonian denies any knowledge of this.
While some of these may be far fetched, there is enough evidence to suggest Europeans and Asians had traveled to America prior to Leif Ericson. And it really isn't that far fetched. I don't doubt that Phoenicians could have sailed to the Americas. The evidence of sculptures with facial features of Asians, Africans, and Europeans seems to indicate travelers from other continents visited the Americas in the ancient past. It's also possible some travelers to the Americas didn't return to their original homes, thus meaning their stories didn't make it back home either. If their stories weren't told, then the stories couldn't have been passed down over time. So the idea of visitors to America in the ancient past isn't to far fetched.