The Americans defeated Panama 1-0 and El Tri beat Honduras 2-0 in Wednesday's semifinals, setting up another championship final between the two power teams of the CONCACAF region.
Mexico and the U.S. have won nine of the 10 Gold Cups contested since the biennial tournament took its current form in 1991. The United States beat El Tri 2-1 in 2007, and Mexico won 5-0 in the 2009 final.
"We know what the U.S. represents," Mexican forward Aldo de Nigris said. "We know it will be a tough rival, but we have to worry about ourselves, and, for me personally, it provides extra motivation because I've never played one of these finals."
Before the Americans could think about Mexico, they had to redeem a stunning loss to Panama on June 11.
Clint Dempsey scored in the 77th minute off an assist from Landon Donovan, and the Americans earned a 1-0 victory on Wednesday. The United States has shut out its last three opponents since the 2-1 loss to Panama in the group stage.
"It was a really good team effort," American coach Bob Bradley said. "It was a hard game, for sure. I thought the mentality of the group was looking for ways to win."
Freddy Adu made a long-awaited return to American soccer in the second half, and set up the winning play with a long, slanting pass to Donovan, who played in his 27th consecutive Gold Cup match to extend his own record.
Donovan was benched at the start for the second straight game, and joined the action in the second half. He tracked down Adu's cross, then threaded a pinpoint pass through the Panama defense to Dempsey, who slid as he redirected the ball into the low corner of the net.
"It was a great ball from Freddy to open up Landon," Dempsey said. "All I had to do was put my foot on it."
Panama lost to the Americans in the knockout stage for the fourth straight time. Coach Julio Dely Valdes said his team surprised the Americans in their earlier match, and the U.S. team was more focused this time.
"It was a very intense game, very few chances for both teams," Dely Valdes said. "I'm pleased with my team's performance, they fought until the very end."
Adu played for the national team for the first time since 2009. Bradley said Adu struggled in early practices for the tournament, but has steadily regained his form.
"From the start of this camp, Freddy's made progress," Bradley said. "The opportunity (Wednesday) was earned on his part. You could see him getting sharper, his confidence coming back. He was a nice part of the play that led to the goal. It's important for him, he earned this opportunity and I think everybody on this team feels good about that."
The United States is unbeaten in 22 of its last 24 games in the Gold Cup, a tournament with 12 teams from Central and North American and the Caribbean. The Americans improved to 7-1-2 against Panama all-time.
Mexico is the only team to have beaten the U.S. in the knockout stage of the Gold Cup, with wins in 1993, '98 and 2009. And the Mexicans have looked more dominant so far in this tournament, outscoring their five opponents by an aggregate score of 18-2.
Mexico had trouble with Honduras in the semifinal, with neither team scoring through 90 minutes of regulation.
De Nigris and Javier "El Chicharito" Hernandez scored off corner kicks early in overtime to propel Mexico into its third straight Gold Cup final.
"This is what we expected," Mexican coach Jose Manuel de la Torre. "Honduras is very orderly, very strong. Our team was not finding the spaces."
Pablo Barrera assisted on both goals for Mexico on Wednesday.
De Nigris headed the first past Honduran goalkeeper Orlin Vallecillo in the third minute of the extra period, drawing roars from the heavily pro-Mexico crowd at Reliant Stadium.
The baby-faced "Chicharito," already a huge star in Mexico, then triggered the loudest cheer of the night when he used his right hip to redirect Barrera's corner kick in the ninth minute of overtime.
Reliant Stadium, home of the NFL's Houston Texans, was packed with green-clad fans of El Tri, and roars went up every time a Mexican player dribbled into the open field.
The announced crowd was 70,627, the second-largest attendance figure for a soccer match in the stadium's history. Last summer's game between Manchester United and All-Stars from Major League Soccer drew 70,728.