There's a legend to that effect somewhere,although I can't cite a source for it(the St. Brendan legend). Regarding linguistic affiliations between European languages and Native American languages,try looking at a book by Barry Fell,called
America,B.C. Fell makes a reasonably good claim for some of the northeastern tribe's words-place names in particular-to have Celtic roots.
In fact,thinking about it,the Albans that Mowatt refers to would-again,assuming they existed-have probably spoke a Celtic based language,since Mowatt places their origin in Gaul.