Replacements for Harlequins prop Joe Marler (concussion) and Northampton Saints fly half Stephen Myler (broken toe), both injured against the Barbarians yesterday (Sunday) will be named in due course.
Northampton Saints flanker Calum Clark (back) and Saracens flanker Andy Saull (dead leg) have also been ruled out with James Gaskell (Sale Sharks) and Jamie Gibson (London Irish) called up.
The age profile of the Saxons has fallen from 25 years, six months in 2006 to 23 years, nine months this summer.
Henry Trinder and Charlie Sharples (Gloucester Rugby), Rory Clegg and Joe Gray (Harlequins), Kieran Brookes (Newcastle Falcons), Billy Twelvetrees (Leicester Tigers), Gibson and Gaskell are all 22 or younger and appear in the tournament for the first time.
But there is also room for late developers and those seeking to re-establish their senior international claims before England team manager Martin Johnson names his preliminary Rugby World Cup training squad on June 20.
Lock Mouritz Botha, 29, has stepped up from junior rugby with Bedford Athletic through Bedford Blues to Saracens and is included in the squad with fellow Aviva Premiership winners Matt Stevens, 28, and Alex Goode, 23.
They are joined by Exeter Chiefs flanker Tom Johnson, 28, whose first season in the top flight was followed by a try-scoring debut in an England shirt in the 38-32 defeat against the Barbarians.
There are just four survivors from the 22 on duty in last June's 38-18 Churchill Cup final victory against Canada - Goode, Young, Kitchener (Worcester Warriors)and Luke Narraway(Gloucester Rugby)- when tries from Goode, Narraway, Nick Abendanon and Jon Clarke, and 18 points from the boot of Myler, saw them home.
"It's a great opportunity for so many young players to test themselves against international sides like the USA and Tonga who are preparing for the World Cup," said Lancaster.
"The players involved against the Barbarians will have taken a lot out of a match against some really experienced internationals and now the challenge is to bind them together with players coming in from the two Aviva Premiership finalists to produce an effective performance against the USA on Saturday."
After facing the USA at Franklin's Gardens, England take on Tonga at Gloucester on Sunday, June 12 (2.30pm). The finals day at Sixways Stadium, the home of the Warriors, is on Saturday, June 18 will pit the Saxons against Canada, Italy A or Russia.
David Attwood (Gloucester Rugby)
Mouritz Botha (Saracens)
Kieran Brookes (Newcastle Falcons)
Jordan Crane (Leicester Tigers)
James Gaskell (Sale Sharks)
Jamie Gibson (London Irish)
Joe Gray (Harlequins)
Tom Johnson (Exeter Chiefs)
Graham Kitchener (Worcester Warriors)
Matt Mullan (Worcester Warriors)
Luke Narraway (Gloucester Rugby)
David Paice (London Irish)
Matt Stevens (Saracens)
Miles Benjamin (Worcester Warriors)
Mike Brown (Harlequins)
Rory Clegg (Harlequins)
Alex Goode (Saracens)
Paul Hodgson (London Irish)
Topsy Ojo (London Irish)
Charlie Sharples (Gloucester Rugby)
Henry Trinder (Gloucester Rugby)
Jordan Turner-Hall (Harlequins)
Billy Twelvetrees (Leicester Tigers)
Micky Young (Newcastle Falcons)