Having established that in worldbuilding for Terrae Vertebrae that:
a) The world in which Vertebrea and the other continents exists has some likenesses to our own world.
b) These likenesses express themselves in Vertebrean society in resembling High-to-Late Medieval Europe. Exploration-wise, I expressed it thusly: There’s
been Marco Polo, but not Henry the Navigator. Suitable to this article I might also say: and certainly not Christopher Columbus.
c) Complicating the entire picture, we have magic - in terms of the mage's craft and the prophet's blessing, elder races that have some relatively stable intercourse with humanity and more.
So: the titular problem. How can we have the existence of a New World (or indeed, any set of remote continents that may or may not resemble the Americas) in Terrae Vertebrae (or any comparable setting) that specifically has that 'undiscovered lands' feel comparable to the real events of discovery and exploration - and whatever that might bring in its wake - How can we have that when the magicians have known of the continent for centuries thanks to scrying glasses (or whatever magic one deems appropriate to bring news of other lands)?
To ward off the question at the pass, yes one can imagine Leif Erikson existing in Terrae Vertebrae. But there's a distinction between that and the whole business of the Colombian Exchange and settlement.
Well, this may not effect one's players unduly. But one rather likes things to be complete, as the creator.
One answer is to just say that there is another place on the maps very far away that people from Vertebrea don't visit with any kind of regularity. European contact with China and the Far East was not unknown, but not frequent in the same way as it would be after the voyages of the Portuguese. The same idea can be applied to Pseudo-America; no regular route is known, but suitably potent wizards can teleport out that way occasionally and bring back wild tales (incidentally, perhaps this is why only wizards are seen smoking!)
The other, perhaps, is to say that, yes, wizards know about it (scrying, teleporting, psychic contact with Pseudo-American magic users of one stripe or another) but that wizards are notoriously unreliable. Nobody believes them, and even if the Archmage has tea with his pseudo-Incan counterpart every Thursday they discuss the goings-on of the astral realm and the methods and means of magic rather than hashing out trade deals and sending out diplomatic missions. Moreover, the geographical knowledge one gains from such matters is limited, like not being able to zoom out terribly far on Google Maps or some similar software. Yes, one could connect lots of little images together - but it would take excessive time and effort, and magic is rarely entirely reliable.
Until somebody more commercially-minded comes back with a hold full of gold, tobacco, potatoes and the natives of Pseudo-America (in chains or otherwise) - and indeed, then goes and repeats the trick - the entire question is moot.
There are hardly the only answers, I suppose. But these are mine. The whole thing bounces off my "Wizard is a Journeyman" concept that I have written of previously that allows the world of Vertebrea to remain relatively similar to our own - except where and when one wants it to erupt in magical display!