London Irish captain Bob Casey scored his first Test try on an afternoon of few highlights for Declan Kidney's Ireland side in Santa Clara, California.
The Grand Slam champions, missing a host of first-choice players due to the Lions tour and Leinster's Heineken Cup success, finished off their two-match tour of North America with an uninspiring 27-10 victory over the USA Eagles.
Casey barged over off a 13th-minute lineout maul to hand Ireland an early lead, which they boosted to 13-0 in first-half injury-time when new centre Ian Whitten finished off a breakaway attack.
But the US, who included six debutants in their starting line-up, were very keen to impress new coach Eddie O'Sullivan and they proved sticky opponents for an off-the-boil Ireland.
A lot of their good work was undone by a very poor place-kicking display from their number 10 Mike Hercus, who missed four kickable penalties.
Referee Chris White awarded the tourists a penalty try, 13 minutes into the second half, to almost put the game beyond the Americans' reach.
But, inspired by replacement out-half Ata Malifa, they launched a spirited fightback. Malifa dropped a goal and then set up centre Roland Suniula for a converted try.
With the gap down to 20-10 and both sides tiring, Ireland needed a final score to secure their second tour win and they got it when replacement scrum-half Eoin Reddan freed up tour captain Rory Best for a muscular burst to the line.