So sorry dear heart, but they were 421 years too late to be the first for sure. One things this does show is that our ancestors moved around a lot more then we think.
The Vikings would have stayed if the little ice age hadnt hit but the rest just stopped by for a visit before going on their merry way. As for Cristobol Colon, timing is every thing.
One thing is sure: Columbus did discover the western hemisphere and is the only one who established his claim. Maybe the Chinese were before him; maybe the Portuguese were, and surely the Vikings were, BUT, the continous link between east and west begins in 1492. Given the ingenuity of men as sailors, it is quite possible that small expeditions reached the west from both Asia and Europe as long ago as the Ice Age. BUT We don't know, for sure, who or exactly when or where they landed. We have forgotten more history than we remember.