Adams put the U.S. ahead in the 45th minute when he received a pass from Weston McKennie, took a touch and curled a shot that just eluded the right hand of diving goalkeeper Guillermo Ochoa.
Reyna added a 63rd-minute goal following a pair of extra-time assists in Thursday’s semifinal win over Jamaica.
The United States stretched its unbeaten streak against Mexico to seven games since a September 2019 defeat, including five wins.
The match was suspended twice by Canadian referee Drew Fischer because of homophobic chants among the mostly pro-Mexican crowd of 59,471 at AT&T Stadium. He stopped play in the 88th minute, resumed after a 4½-minute wait, then halted it again six minutes into stoppage time. Play restarted 1½ minutes later.
Last year’s Nations League semifinal in Las Vegas was ended about four minutes early because of chants from Mexican fans, who for years have directed a slur at opposing teams’ goalkeepers.
Troubled by a right hamstring injury that twice required surgery, Adams had not played for the U.S. since the 2022 World Cup before entering in the 63rd minute Thursday, then leaving in the 100th because of a minutes restriction.
He was limited to a single 21-minute club appearance between March 11, 2023, and this past March 13, when he returned from the injury with a 20-minute stretch for Bournemouth against Luton in England’s Premier League.
Adams’ joined Josh Wolff as the only Americans in the last 40 years to score their first two goals against El Tri. Adams also scored in a friendly against Mexico in September 2018.
Still on a minutes limit, Adams was replaced by Johnny Cardoso at the start of the second half.
Reyna, limited to one league start this season for Borussia Dortmund and Nottingham Forest, scored his eighth international goal. Christian Pulisic’s cross was blocked by defender Johan Vásquez. The ball deflected off American forward Haji Wright back to Vásquez, who headed a clearance attempt. Reyna let the ball bounce and beat Ochoa to the near post from 16 yards.
Fischer initially awarded a penalty kick for a challenge by Antonee Robinson on Santiago Giménez, but following a video review by Nicaragua’s Tatiana Guzmán, Fischer called off the foul and gave the forward a yellow card for simulation.
Ochoa, Mexico’s 38-year-old captain, made his 150th international appearance. Seams were visible in the temporary grass strips installed on the field of the NFL’s Dallas Cowboys.
U.S. coach Gregg Berhalter made five changes from Thursday’s starting lineup in the 3-1 extra-time win against Jamaica, adding right back Sergiño Dest, central defender Tim Ream, midfielders Tyler Adams and Gio Reyna, and forward Haji Wright. They replaced Joe Scally, Miles Robinson, Yunus Musah, Malik Tillman and Folarin Balogun.
No players from Major League Soccer started.
Mexico coach Jaime Lozano inserted right back Jorge Sánchez and forward Hirving Lozano for Julián Araujo and Julián Quiñones.
Jamaica beat Panama 1-0 in the third-place game on Dexter Lembikisa’s 41st-minute goal.