Republic of Ireland 2 USA 1
Clifford (pen) 31
Ireland will now meet tournament hosts Northern Ireland in Friday's final after they completed the other group in top spot following tonight's 1-0 victory over Switzerland.
Greg Cunningham headed Ireland in front after 18 minutes following an excellent cross from the left by Conor Henderson.
Ireland were awarded a penalty on 31 minutes when Henderson's attempted cross was handled in the box and Irish captain Conor Clifford converted the spot-kick to make it 2-0.
The USA cut Ireland's lead six minutes later with a goal to boost their hopes of claiming a draw but Ireland were they stronger team in the second half.
Ireland's best chance of adding another goal fell to Conor Henderson with twelve minutes left whose powerful shot rebounded back off the crossbar.
Goalkeeper Chris Oldfield, who earned his second cap for Ireland tonight, produced a spectacular save from point-blank range in the last minute.
Republic of Ireland Team v USA
Chris Oldfield - Liverpool
Neil Harney - Belvedere
John Dunleavy – Ballybofey United
Mark Connolly – Monaghan United
Conor Hourihane – Douglas Hall
Aaron Doran – Blackburn Rovers
Conor Clifford – Crumlin United
Paul Corry - Belvedere
Conor Henderson - Arsenal
Greg Cunningham – Mervue United
Karl Sheppard - Shelbourne
Richie Towell (Crumlin United) for Harney (40 mins), Niall Byrne (Home Farm) and Jason Hughes (Geraldines) for Connolly and Doran (both 41 mins).