John Hackworth's young American side must be wondering how they failed to win their opening tie by several goals.
Axel Levry, who played wide on the right, blasted a half volley into the top corner to give them the lead after ten minutes of gentle sparring and after that the shots rained in on the Portuguese goal.
Ellis McLoughlin at centre-forward could have notched a hat-trick before half-time, three rasping shots from near the edge of the box missing the target by inches.
There was a brief respite as Evandro stretched for Rui Almeida's low ball in from the right and produced an effort that was superbly saved one-handed by Josh Lambo - but the American pressure was almost relentless.
They were clearly the fitter team and moved the ball around so quickly that the Portuguese were forced to defend in numbers.
The picture was little different in the first part of the second half, with Ruca leaping to hold a Jared Jeffrey header from a free-kick and then a swerving left-footer from Daniel Barerra.
Each team made substitutions in the final period of the match and Bryan Dominguez, a livewire midfielder who seemed to start most of the Americans' attacks through the middle, was one of the players withdrawn.
Portugal came more into the match, forcing Lambo to make a couple of spectacular stops, and hitting the bar with a 35-yard free-kick from Oscar Sa that the 'keeper seemed to think was going over.
They piled forward in the last five minutes, throwing caution to the wind, and skipper Dinis's firm shot from inside the box was deflected past Lambo for the equaliser.
One-one would have been an improbable result for most of the afternoon.
USA: Lambo, Williams, Lee, Turk, Uy, Wenzel, Levry (King), Jeffrey, McLoughlin, Dominguez (Gracia), Barerra (Zimmerman).
Portugal: Ruca, Coelho, Sa, Simoes, Nunes (Goncalves), Dinis, Rui Almeida (Torres), Martins, Evandro, Bolinhas (Ferreira), Cristiano
Referee: K Hill
Attendance: 70