Who cares, apparently the Chinese didn't find it good enough to come back. Leif Erikson was here too in 1000 AD and that really doesn't matter either. People actually came back after Columbus.
And the Irish were probably here around 800 AD. As you said, Columbus made something of it the others are interesting historical footnotes.
And THAT is the key point. It took the Spanish & Portuguese -- followed by the English & French -- to integrate the western hemisphere with the rest of the "civilized" world. A chance visitation without lasting documentation really doesn't 'count'. BTW, I think the Vikings & possibly the Irish were here before Columbus. But I think that Columbus deserves the credit.