A terrible start from the Irish saw them concede two quick fire tries to the Americans, and they could never recover from the 14-0 lead that their opponents took within fourteen minutes when Phaidra Knight and Erin Carter touched down twice with Kristin Baja converting.
However the Irish did claw their way back into contention with a penalty from Grace Davitt before the break and while their set-piece was again hit and miss, their overall play was hugely improved from their display against France earlier in the week.
Baja put the USA further out in front when she skipped over just after the break but Gillian McAllister put Ireland right back in the hunt with a try on 53 minutes following sustained pressure on the American line, with the Ulster prop crashing over from a close range line-out.
Davitt then knocked over her second to push the score to 19-11 and suddenly with less than ten minutes to go Ireland were searching for a score that would give them a bonus point to claim their first of the tournament.
They almost clinched it with less than a minute to go but America turned over possession from a lost line-out and Knight had a clear run to the line to make it 24-11.
Irish coach Philip Doyle said his side would rue their early concession of scores.
"They started very well and that was hard to come back from. The USA are one of the world's strongest teams but we are disappointed as they were there for the taking. We are going into the South African game though with huge confidence because the girls did stand up tonight and the time will come when we are knocking the big nations in this sport."
Ireland play South Africa on Friday in their last pool game after which sides are seeded and paired to determine final placings. The Irish team are to travel to the Rockies tomorrow for a leisure day.
In another game with an early kick-off, defending champions New Zealand hammered Samoa 50-0 with fulback Amiria Marsh claiming a hat-trick to become the tournament's leading scorer.
J O Sullivan, J Feighery, L Cantwell, G Davitt, A Greensmith, SJ Belton, T Rosser, F Coghlan, Y Nolan, G McAllister, C Mahon, G Healy, O Brennan, R Boyd, J Neville
Replacements: J Lonergan (for Y Nolan 48), M Barrett (for G McAllister 58), R Foley (for G Healy 79), E O Sullivan (for O Brennan 63), N Ni Chaidhain (for SJ Belton 77)
Referee: Christine Hanizet
IWRFU Press Officer