Their 1-0 win over North Korea clinched the Group G title, the first time the Americans, three-time gold medalists, had finished the first round at 3-0-0. They also were playing in the first international women's soccer game and the first match in 23 years involving women at the home of Manchester United.
Fittingly, striker Abby Wambach scored the lone goal as she and her teammates staged a unique goal celebration. The Americans hope there will be more to celebrate as they will play New Zealand in the quarterfinals in Newcastle on Friday.
"It's now or never -- lose and you go home," Wambach said. "But this is the fun part. This is what it is all about. We came here for the gold medal and that's what we want to go home with."
The game made history on several levels.
"It was awesome," Wambach said. "So many U.S. fans specifically came to watch at Old Trafford. It was a dream come true for a lot of us. It's amazing to have gotten a goal."
In 1989, the last time a women's game was staged here, there were 914 fans on hand. Tuesday, 29,522 saw Wambach score in the 25th minute as she slotted home Alex Morgan's feed past goalkeeper O Chang Ran.
Goalkeeper Hope Solo and captain Christie Rampone then flopped to the ground with the other nine players joining hands, wriggling their arms like a giant worm and pointing to the pair of players doing the funky dance move from the 1970s and '80s. It was part of a birthday present for Solo, who turned 31 Monday.
"I think Hope chooses and prefers the wins and the shutouts as birthday presents," Wambach said. "It was great to get her involved. It makes us feel what the game is about. It's about fun. It's about laughing and enjoying it out there. How often are you going to say that you played at Old Trafford and scored a goal?"
If there was a concern, it was the drop in the team's energy level from the first to second half. The Americans dominated as the Koreans rarely penetrated into enemy territory in the opening 45 minutes. But Team USA was much more subdued after the break.
"We wanted to save our legs because the next game is going to be really important," Wambach said.
Solo, who hasn't surendered a goal in 256 minutes, wasn't severely tested. "All we needed was a tie, so our energy was a little low," she said. "We know how to pick it up and rise to the occasion. It's about peaking at the right time."