So, I tracked down the offending passage by searching sources systematically. The direct source appears to be the late Native American scholar-activist Jack D. Forbes’ (d. 2011) Africans and Native Americans (1993), cited under a different title by Loewen. There, Forbes claims that the following passage from Pliny the Elder (Natural History 2.67), citing a lost work of the earlier Cornelius Nepos (c.100 BCE-c. 25 BCE), proves that Native Americans reached Europe. I have substituted a standard translation for Forbes’ partial and incomplete one.
“The same Cornelius Nepos, when speaking of the northern circumnavigation, tells us that Q. Metellus Celer, the colleague of L. Afranius in the consulship, but then a proconsul in Gaul, had a present made to him by the king of the Suevi, of certain Indians, who sailing from India for the purpose of commerce, had been driven by tempests into Germany.”
We are asked to assume that Cornelius Nepos was wrong about the sailors being Indos (from India) while also apparently accepting that they had no difficulty communicating with the Suevi of the Rhineland. Did German tribes speak Mexican languages?
“When he [Celer] was proconsul in Gaul, he was presented with certain Indians as a present by the king of the Boti; asking whence they had come to these lands, he learned they had been seized by a storm from Indian waters, that they had traveled across the regions between, and at last landed on the German shores” (my translation).
Forbes, however, did not originate this claim. In 1900 Peter de Roo wrote the same thing in his History of America before Columbus, and Forbes follows Roo’s arguments point for point, down to the claim that Celer (and thus Nepos) mistook the Native Americans for people from India because of their “Asiatic features.”
But de Roo didn’t originate the claim, either. The claim derives, ultimately, from the work of the Spanish historian Francisco López de Gómara, who in his Historia de las Indias (chapter 10), suggested that the Romans had been “deceived by the color” of Native Americans from Labrador who had been carried across the North Atlantic. Gómara, of course, was merely speculating; he is the same man who in the same book argued that the Americas were identical to Atlantis because the Aztecs had words that used the letters “atl”: “But there is no dispute or doubt what was the island of Atlantis, for the discovery and conquest of the Indies simply clarify what Plato wrote of those lands, and in Mexico they call water atl, a word that seems like, if it is not already, from the island” (chapter 220; my translation). He did not write from evidence, merely speculation, in order to provide Classical antecedents to justify the Spanish conquest of the Americas. He was criticized even in his own lifetime for the inaccuracy of his work.
Georg Hartwig, in 1860, following the earlier work of Alexander von Humboldt, suggested that the Gulf Stream could have carried some unfortunate Inuit from America to Northern Europe, accounting for Nepos’ report. This is certainly possible, but it is probably the least likely of situations since Cornelius Nepos and the later Roman writers seemed to find nothing particularly noteworthy about the Indians in Germany, implying they were garden variety Indians from India.
In fact, the Journal of the American Geographical Society of New York noted in 1891 that Pliny, writing in 77-79 CE, merely repeated the statement of Mela from 43 CE, and Mela in turn has a notoriously error-ridden manuscript tradition. It may well be, the Journal argued, that a copyist’s error transformed into “Indos” the original word “Irenos” (Irish) or even “Iberos” (Spanish), making this a perfectly plausible story of a Celtic shipwreck on German shores that Mela and then Pliny misunderstood. Earlier scholars, recognizing the clear evidence for Roman contact with India and vice versa, argued that Nepos’ account was garbled and that the Indians had arrived in Germany not by sea but by a different route. Rabelais differed, suggesting that the Indians had circumnavigated Africa, while Vivien de St. Martin argued that they were Wends, a Slavonian people from the Baltic who could have been mistaken for Indians because the Romans believed in a nonexistent water route between the Baltic and India. Quaintly, the Late Antique writer Martianus Capella (The Marriage of Philology and Mercury 6.621) completely misunderstood the entire textual tradition and transmitted to the Middle Ages the false notion that Nepos had kidnapped Indians and sailed with them past Germany!
The long and short of it is that there is no independent confirmation that Native Americans washed up in Holland in 60 BCE as the internet claims. When examined carefully, the texts on which this claim rest simply do not provide sufficient evidence to justify a claim that, frankly, exists mostly due to Columbus’s misidentification of Native Americans as Indians, calling Gómara’s attention to Pliny’s passage. Had Mela and Pliny named anyone other than the Indians of India, no one would ever have batted an eye at Nepos’ report. There is no reason to do so now in service of an imaginary trans-Atlantic crossing that lacks any other evidence to support it--especially when there are so many more plausible explanations.
We can't rule out an accidental shipwreck of Inuit, but the evidence from the brief passages now extant argues against it. And we certainly cannot get from the extant texts the exact number of two, uncontested proof they were Native Americans, or a clear indication they landed in what is now the Netherlands. Thus, on almost every point, the claim as currently presented in alternative, Afrocentrist, and diffusionist literature is demonstrably false.