The final score was USA 30, Scotland 29, after the visitors conceded two tries to Worcester hooker Joe Taufete'e and a gift score to flanker Hanco Germishuys to throw away a dominant first half with an error-ridden second.
They did give themselves a chance to win the game three minutes after the 80 minutes were up when Adam Hastings found the killer pass to put Dougie Fife, the replacement wing, in for their fourth try, but the touchline conversion proved to be too tricky for Blair Kinghorn.
All that came after the perfect start as new captain Stuart Hogg was given a tiny sliver of space on the outside of the American defence.
He needed no second invitation, slicing through and proving a perfect pass to Kinghorn on the wing for the opening try.
With the young wing converting, it was just the settler they were looking for.
Any idea that it was going to be an easy ride for the Scots was, however, quickly dismissed as the USA started to get their big forwards into the game, pummelling the Scots defence and forcing a string of penalties.
The big win for USA was also anchored by a strong performance from Alan MacGinty, who converted all three tries and kicked three penalty goals.