The inclusion of Ross means Tony Buckley moves from the right side of the scrum to loosehead prop.
The front row reshuffle sees Tom Court move to the replacements bench to fill the vacancy made by Ross' promotion to the starting line-up.
The rest of the pack remains unchanged with Mick O'Driscoll named in the side despite picking up a slight wrist sprain during the Canadian game last weekend.
As a precaution, Leinster second row Devin Toner has been called into the squad.
Toner, who was also named in the Churchill Cup squad, will join up with the senior squad later today (Wednesday) and will remain on with the other members of the panel who will be taking part in the Churchill Cup in Denver which begins in early June.
Another addition to the squad is Alan Gaffney, who was involved with Leinster's Heineken Cup win on Saturday.
He will be now working in his Ireland capacity as backs coach for the remainder of the tour and the Churchill Cup.
Head coach Declan Kidney said: "We felt that after last week's game against Canada that the players who started deserved another chance to improve on that performance.
"We thought long and hard about making further changes to the side, but with only two full training sessions under their belts before the Canada game, we thought that it would be better to give an opportunity for the same players and combinations to find their feet a bit more with some more sessions to work off.
"This tour and also the Churchill Cup is all about building a base of experience with the national coaches and it is particularly tough on the players not selected in the starting team as they have been training just as hard as the players picked and were pushing for inclusion this week.
"The majority of those who will not start on Sunday or are not in the matchday 22 will all have further opportunities in the Churchill Cup."
Tour captain Rory Best said: "We need to lift our levels from the Canada game if we want to put in a performance that can put us in a position to win.
"There was a little lack of cohesion in Vancouver which was possibly down to the number of new combinations and the eight new caps we had.
"The game on Sunday gives us a chance to build on last week and will require another huge effort in work rate to allow us to compete with the USA team who will be a real challenge for us playing them at home.
"The conditions have intensified with the heat a big factor as well as the physical threat that the opposition bring to the game."
You can purchase tickets for Sunday's game here.
IRELAND TEAM & REPLACEMENTS (v USA, Setanta Challenge Cup, Sunday, May 31, Buck Shaw Stadium, Santa Clara, kick-off 1pm local time/9pm Irish time (live Setanta Sports Ireland)):
15 - Gavin Duffy (Galwegians/Connacht)
14 - Barry Murphy (UL Bohemians/Munster)
13 - Darren Cave (Belfast Harlequins/Ulster)
12 - Ian Whitten (Ballymena/Ulster)
11 - Ian Dowling (Shannon/Munster)
10 - Ian Keatley (Galwegians/Connacht)
9 - Peter Stringer (Shannon/Munster)
1 - Tony Buckley (Shannon/Munster)
2 - Rory Best (Banbridge/Ulster) (capt)
3 - Mike Ross (Harlequins)
4 - Bob Casey (London Irish)
5 - Mick O'Driscoll (Cork Constitution/Munster)
6 - John Muldoon (Galwegians/Connacht)
7 - Niall Ronan (Shannon/Munster)
8 - Denis Leamy (Cork Constitution/Munster)
16 - Sean Cronin (Buccaneers/Connacht)*
17 - Tom Court (Malone/Ulster)
18 - Ryan Caldwell (Dungannon/Ulster)
19 - Donnacha Ryan (Shannon/Munster)
20 - Eoin Reddan (London Wasps)
21 - Niall O'Connor (Belfast Harlequins/Ulster)*
22 - Denis Hurley (Cork Constitution/Munster)*
NB: *denotes uncapped player
Ireland 'A' Churchill Cup Schedule:
Ireland 'A' v Canada, Wednesday, June 10, 4.30pm (local time), Infinity Park, Glendale, Colorado
Georgia v Ireland 'A', Sunday, June 14, 3.30pm (local time), Infinity Park, Glendale, Colorado
Finals Day, Sunday, June 21, Dick's Sporting Goods Park, Denver, Colorado