[stuartcr]

I believe anyone sailing west, towards the setting sun, would have had to discover America eventually.

[Verginius Rufus]

The Norse had colonized Iceland and Greenland and soon afterwards accidentally discovered the mainland of North America (about 986--first attempt to colonize was about 1000).

Cabral in 1500, trying to sail around Africa to get to India, accidentally discovered Brazil--so if Columbus had never sailed, Europeans would have learned about the New World pretty soon anyway.

A couple of Genoese sailed west in 1291, I think it was, and were never heard from again--they could have been lost at sea, or perhaps reached America. Maybe they were eaten by Caribs.