Forwards Will Johnson (London Irish), Mike MacDonald (Leeds Carnegie) and Shawn Pittman (London Welsh) are joined by backs Junior Sifa and Tim Usasz who both play for Nottingham.
The USA take on England Saxons at Northampton's Franklin's Gardens on June 4 and Tonga at Moseley Road, Esher, four days later and then finals day at Worcester's Sixways on June 18.
The USA will aim to finish as high as possible in their pool which will determine whether they play for the cup, bowl or plate on finals days, with Canada, Italy and Russia in the other group.
The USA squad consists of 13 overseas-based players, while seven members of the squad are currently in the UK representing the United States in the HSBC Sevens World Series.
O'Sullivan said "The fact that there are some players resting gives an opportunity to others to make a case for inclusion in the final selection for Rugby Word Cup."
USA squad
Forwards: Inaki Basauri (L' Aquila), Chris Biller (San Francisco Golden Gate), Todd Clever (Suntory Sungoliath), Pat Danahy (Life University), Eric Fry (Las Vegas Blackjacks), JJ Gagiano (University of Cape Town), Nic Johnson (unattached), Will Johnson (London Irish), Danny LaPrevotte (San Francisco Golden Gate), Scott LaValla (unattached), Mike MacDonald (Leeds Carnegie), Shawn Pittman (London Welsh), Louis Stanfill (Mogliano), Phil Thiel (Life University), John van der Giessen (Utah Warriors).
Backs: Paul Emerick (Life University), Tai Enosa (Belmont Shore), Troy Hall (New York Athletic Club), Colin Hawley (Olympic Club), Nese Malifa (Glendale), Mike Palefau (Utah Warriors), Mike Petri (New York Athletic Club), Mile Pulu (San Francisco Golden Gate), Junior Sifa (Nottingham), Andrew Suniula (Chicago Griffins), Roland Suniula (Boston Rugby), Kevin Swiryn (Agen), Zack Test (unattached), Tim Usasz (Nottingham).
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