The difference is that when ole Chris Discovered America it stayed discovered.
So maybe the Tards were here, probably weren’t.
Chris gets the award.
The Americas stayed ‘discovered’ at least as long ago as the 11th century. Columbus took a trip to Iceland as part of his research, and of course made his famous gaffe regarding the circumference of the Earth.
The reason the colonization happened after 1492 is, prior to that time, that nice edge given by firearms didn’t exist. Moving into an area already occupied, against a population with analogously advanced weaponry, didn’t work so well.
And the natural climate change cycles produced conditions that either encouraged or hindered travel, and led to increases and decreases in population.