Apparently the Atlantic and to a lesser extent the Pacific were well travelled thoroughfares for millennia. Columbus brought it to the attention of rulers who thought to get rich and powerful from the discoveries and thus actually brought the Americas into the Western World.
I often wonder if past visitors may have brought diseases that raged through the much larger mesoamerican populations of the past wiping them out.
Diseases passed from mesoamericans to Europeans would have a harder time making it back to Europe or Asia. The ancient travelers may have died here or died during the return sea voyages.
I don’t remember the names but I’ve read about a tribe in Chile that uses a pottery decoration pattern that is very similar to traditional patterns used by the Ainu of northern Japan. The patterning similarities could be purely coincidental but only the South American tribe and the Ainu carry a certain mild genetic disease found nowhere else in the world. The Ainu carried the gene for as long as anyone can tell but it appeared suddenly in the south American tribe within the last 2000 years or so. (right around the time the pottery patterns appeared)