Calif Bill wrote:

Columbus may have had charts of parts of the Americas. The fisherman had
followed the birds and fish for years, so there was a lot of knowledge. The
Norsemen had a colony in Nova Scotia area for awhile.

An underappreciated aspect of Columbus' voyage is that he had a pretty
fair idea just exactly where he was going.

As you note, fisherman, the Norse, and others had been voyaging to NA
for centuries prior to 1492. It wasn't much of a secret that there was
land to the west. Every educated person knew the world was round long
before 1492, and there were some remarkably accurate estimates of its
size. It wouldn't take a genius to realize that the land reported by
the Norse, by cod fishermen, etc were too close to be Asia and India.

Biggest problem that Columbus faced was getting financing from "Their
Most Catholic Majesties" in Spain. The official position of the church
in the 15th Century was that there could not possibly be another
continent or continents to the west as there was no mention of such
land masses in the Bible. The fear was that if things that were not
addressed in the Bible were discovered, the general public might begin
to question whether the Bible, the Pope, and the Church were really
infallible. And that wouldn't do at all -not with the Spanish
Inquisition just getting under way, etc.

By promoting his voyage as an attempt to reach "India", (which was
recognized by the church), he didn't run afoul of the official church
dogma.

And yes, there is a lot of evidence of cultural exchange between China
and Mexico, as well as between people indigenous to the Pacific Islands
and native Americans of the Pacific NW. One look at the similarities
between a Pacific NW story pole (popularly called "totem poles") and
some of the carvings from Polynesia reveals some similarities that are
either the result of cultural exchanges or a truly *amazing*
coincidence.