You could take a small chunk of the Great Divide, Colorado Trail or AZ Trail and call it a classic, easy ride. There would be, literally, dozens upon dozens of possible “classic rides” in just those three routes.
Not sure of the gist of your piece, but it seems like trying to create a sort of best-of survey of US trails would be a daunting (if not dubious) task. Good luck!
Any relation to Adventure Cycling media kingpin Mac McCoy?