Paul Lambert's side fly out to Philadelphia as it prepares for games against the Union and two other MLS sides in the Chicago Fire and Portland Timbers.
There is no place in the 25-man party for Scotland defender Alan Hutton or midfielder Jean Makoun, who looks set to leave the club. Winger Marc Albrighton, who recently returned from a thigh injury, also misses the trip.
But Fabian Delph, another to be linked with a move away from Villa Park, will travel to the US.
Goalkeeper Shay Given and defender Richard Dunne are selected after their Euro 2012 appearance for the Republic of Ireland, while the young Irish duo of Enda Stevens and Samir Carruthers also make the party.
Aston Villa squad for three-match tour of the United States: Agbonlahor, Baker, Bannan, Bent, Carruthers, Clark, Collins, Delfouneso, Delph, Dunne, El Ahmadi, Given, Gardner, Guzan, Herd, Holman, Ireland, Johnson, Lichaj, Lowton, Marshall, N'Zogbia, Stevens, Warnock, Weimann.