The US is dominating the game at the midway point of the first half after taking the lead with a well-taken finish by forward Sophia Smith.
Smith, who is playing in her first World Cup match, scored off a great through-ball from veteran Alex Morgan.
The energy in the crowd is high following the goal, with dueling chants of “Vi-et-nam!” and “U-S-A!”
US fans have also been cheering “I believe that we will win!”
The US team has maintained most of the possession but Vietnam has had a few offensive plays.
