Alex Morgan gave the U.S. its first lead of the night in final seconds of the second overtime. Her 6-yard header, on a long cross from Heather O'Reilly, looped high into the net over goalkeeper Erin McLeod for the winning goal.
The Americans will have a chance to avenge one of the most gut-wrenching losses in the program's history. The players have been eyeing a rematch with Japan after losing to Japan on penalty kicks in the World Cup final last summer.
The U.S. will play Japan for the gold medal on Thursday.
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In women's pole vault, Jenn Suhr of the U.S. won gold, ending Russian Yelena Isinbayeva's bid for a third straight Olympic title. Suhr won after clearing 4.75 meters at her second attempt.
U.S. Olympic fighter Nick Delpopolo was disqualified Monday after testing positive for a banned substance. The 23-year-old from Westfield, N.J., says he unintentionally ate something baked with marijuana before the games.
Delpopolo finished his judo competition last week, placing seventh in the men's 73-kilogram weight class.
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The International Olympic Committee disqualified Delpopolo after failing an in-competition doping test. Delpopolo is the first of the 10,500 London Games athletes to fail an in-competition doping test. Prior to competition, four other athletes were banned from games for testing positive for a banned substance. The IOC started its London testing program in mid-July.
"I apologize to U.S. Olympic Committee, to my teammates, and to my fans, and I am embarrassed by this mistake," he said in a statement released by the U.S. Olympic Committee. "I look forward to representing my country in the future, and will rededicate myself to being the best judo athlete that I can be."
The disqualification means he will lose his diploma, and everyone who finished behind him moves up one slot.
In men's beach volleyball, Americans Jake Gibb and Sean Rosenthal were knocked out of the tournament by Latvia. The Americans won the first set 21-19, then dropped two straight to Martins Plavins and Janis Smedins, 21-18, 15-11.
The other American men's team, Beijing gold medalists Todd Rogers and Phil Dalhausser, had already been eliminated.
Aliya Mustafina gave Russia its first gold in women's gymnastics, capping an impressive comeback from a serious knee injury on uneven bars.
"I was hoping very much I'd done everything I could to win it," Mustafina said.
The Americans, meanwhile, went home empty-handed on Monday. All-around champion Gabby Douglas finished last on uneven bars, while Sam Mikulak finished fifth on vault.
"Toward the end of the Olympics, you get mentally and physically tired and you're just like drained," Douglas said. "I tried to fight through it as much as I could."
An Olympic spectator accused of hurling a plastic bottle onto the stadium track seconds before the men's 100-meter final pleaded not guilty Monday to creating a public nuisance.
Police said Ashley Gill-Webb is alleged to have also shouted abuse before hurling the bottle just before the race began.
Usain Bolt, the Jamaican sprinter who won the race in an Olympic-record time of 9.63 seconds, said he was unaware of the incident. However, U.S. sprinter Justin Gatlin, who won the bronze medal, said he had been briefly distracted.
"When you're in those blocks and the whole stadium's quiet you can hear a pin drop," Gatlin said, acknowledging he had heard the bottle land. "You can't complain about that, the race went on and it was a great race."
Check out photos of the 2012 London Olympics competitions
The Associated Press contributed to this report.
