Captain Chris Wyles was moved to fullback after two games on the wing and Thiel replaced Zach Fenoglio, who started in the Americans' opening 25-16 defeat against Samoa.
"The scrum was once again a good platform of attack and the lineout had a few hiccups, which was unfortunate as it cost us on four occasions," coach Mike Tolkin said in a USA Rugby statement on Friday.
"Fenoglio's logged a lot of minutes as starter and Thiel is a little fresher. They are both very good and virtually even, so we thought this was a good time to get Phil in as a starter and have Zach add punch off the bench."
However, it is with the U.S. running game that Tolkin hopes to hurt the Scots.
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"We have the capability to do some dynamic things with ball in hand, with both power and pace," he said. "We'd like to be able to make this a more consistent, potent weapon. Scotland, like everyone, has weaknesses and we need to exploit them effectively with both of those tools."
Team: 1-Eric Fry, 2-Phil Thiel, 3-Titi Lamositele, 4-Hayden Smith, 5-Greg Peterson, 6-Al McFarland, 7-Andrew Durutalo, 8-Samu Manoa; 9-Mike Petri, 10-AJ MacGinty, 11- Blaine Scully, 12-Thretton Palamo, 13-Seamus Kelly, 14-Takudzwa Ngwenya, 15-Chris Wyles (captain)
Replacements: 16-Zach Fenoglio, 17-Olive Kilifi, 18-Chris Baumann, 19-Cameron Dolan, 20-John Quill, 21-Danny Barrett, 22-Shalom Suniula, 23-Folau Niua
(Compiled by Ed Osmond; Editing by David Goodman)
