Is it possible that some Africans were in the Americas predating Columbus? I suppose it's possible. There's evidence that some Europeans, Leif Ericson, reached the continent 500 years before Columbus. There's evidence that Native Americans are genetically related to Asians. So, it's possible that there were some Africans or African ancestry that also touched on the Americas. I'd be surprised if the numbers were large though. And I think it would be a stretch to classify them in the same boat as later Africans. The same way we don't classify Native Americans as Asian, despite the much stronger scientifically linked connection.
The unfortunate thing about the Americas and modern history is that so much of the early population died without entering into the annals of written history. An estimated 90% of the indigenous population died, who knows what they looked like, acted like, etc.