Solutions are somewhere down the road a ways. One starts uncertain of the alphabet, or writing system, for not all are alphabets, then of the language, and only then can decipherment begin. And even then there is resistance to there being any writing in America, except for Mexico of course, and even that was not alphabetic. All else is suspect. But it should not be.
Evidence is evidence.
An alphabetic inscription or other writing in America is evidence, and the notion that it should not be here is only opinion. The inscriptions exist, on rocks with datable weathering phenomena, and accompanied by masses of other evidence. Plants and animals were carried back and forth across the Atlantic and the Pacific, and ideas surely accompanied them. I have not tried to document all of this. I read it at the time, lost track of the article, and then found it amongst my accumulation of back numbers.