The Americans had a 15-3 shot advantage, but couldn't find a way to beat goalkeeper Tiarna McKenna.
"We played well, created chances, and dominated the game, but failed to put anything away," said U.S. head coach Bill Irwin. "Northern Ireland made the game difficult. They got numbers back and they certainly battled for 90 minutes."
A game against Ireland's national team was canceled and the U-23s will instead play an Irish women's select team in its second and final game of the tour.
May 15 in Belfast
USA 0 Northern Ireland 0.
USA -- Arnold, Barnes, Taylor, Fowlkes, Reynolds (Tsao, 52), Press, Wright, Hawkins (Oakes, 52), O'Hara (Chandhoke, 58), Schoepfer, Bosio (Bowyer, 65)
Northern Ireland -- McKenna, Gillespie, Nelson, Hutton, Bailie, Caldwell, Mullholland (Timoney, 72), Havelin (Carson, 69), Furness, Vance, Hyndman (Bergin, 35)