The Scots went ahead after only eight minutes as lock Euan McVie going over from a driving maul.
Scotland's second try came 20 minutes later as Glasgow centre Johnny Ventisei touched down under the posts with scrum-half Andrew McLean adding the conversion.
Minutes later back-row Tom Currie squeezed over to give Scotland a 17-0 half-time lead.
Corbin Smith's penalty got the USA on the scoreboard shortly after the interval, but Scotland replied when hooker Jerry Blyth-Lafferty went over behind another maul.
Blyth-Lafferty leapt over the line again from the lineout, with Hocking converting and he did so again after McVie crashed over from short range.
McVie made it a hat-trick of tries minutes later with Hocking kicking the extras.
Centre Kerr Yule added Scotland's final try before winger Keelan Farrell's fine consolation try in the dying seconds.