Diego Luna scored both goals as the United States beat Guatemala 2-1 in St Louis on Wednesday to reach the final of the CONCACAF Gold Cup where they will face Mexico.
Raul Jimenez struck in the 50th minute as Mexico overcame Honduras 1-0 in Santa Clara, California to reach their fourth straight Gold Cup final.
Luna, an exciting talent who plays for Real Salt Lake in Major League Soccer, put the USA ahead in the fourth minute when a Luca de la Torre shot was parried and the 21-year-old pounced to slot home.
The winger, who came up through the ranks of lower-division football in Texas, then doubled the advantage in the 15th minute with a brilliant individual goal.
Luna picked up the ball in midfield and dribbled goalwards, skipping a challenge before firing home from more than 20 yards.
Guatemala striker Rubio Rubin had an effort saved by USA keeper Matt Freese and then another disallowed for offside to the frustration of his team's large and noisy travelling support.
Sebastian Berhalter went close to a third just before the break with a free-kick which deflected off the wall and was well saved by Kenderson Navarro.
Mauricio Pochettino's USA, who came into the tournament on the back of a four-game losing streak, were under increasing pressure from a lively Guatemala after the interval.
It intensified after the Central Americans scored in the 80th minute when Arquimides Ordonez dribbled into the box and 18-year-old Boston-born Olger Escobar fired home.
The home fans held their breath in stoppage time when Jose Morales drilled a low shot from the edge of the box but Freese did well to get down and push the ball wide.
Luna's performances will bolster his chances of making the squad for the World Cup next year even when regular starters such as Christian Pulisic return.
"Every single one of these players think about it the same way I do, that this is the number one dream we had as a kid and we are going to fight to have as many chances to wear (this shirt) as we can," said Luna.
The Californian, of Mexican heritage, was praised by teammate Berhalter for his two crucial goals.
"He does stuff like that, scoring two goals like that in a semi-final, it is why he's him and he's one of the best players in MLS and one of the best players here," he said.
Mexico, looking for a record-extending 10th Gold Cup title, were pushed all the way by an improved and tenacious Honduras but ultimately emerged victorious to set up an eighth final meeting with their North American rivals.
16-year-old Gilberto Mora, the great hope of Mexican football playing just his second game for his country, created the winning goal with some lovely footwork, as he jinked through the Honduras defence before threading a perfect pass to Jimenez.
The Fulham striker made no mistake with a thundering finish to put El Tri in front at Levi's Stadium, the home of the NFL's San Francisco 49ers.
Mexico had the ball in the net again after a free-kick caused chaos and Edson Alvarez turned the ball home but the effort was ruled out for offside after a VAR review.
Honduras pushed forward with increasing desperation in search of a leveller but missed the creative touch in the final third as Javier Aguirre's side held on.