The United States will face holders Mexico in the Gold Cup final after both won their semi-finals on Wednesday.
The US beat Guatemala 2-1 in St Louis, with Real Salt Lake forward Diego Luna scoring twice in the opening 15 minutes.
Mexico booked their spot in the final when Fulham striker Raul Jimenez scored the only goal in a 1-0 win over Honduras in Santa Clara, California.
The US, who are co-hosting the tournament with Canada, got off to a fine start when Luna pounced to put them ahead on four minutes after Guatemala goalkeeper Kenderson Navarro parried a shot from Luca de la Torre.
US midfielder Malik Tillman then went close before Luna collected the ball about 30 yards from goal, ran at a defender and cut inside him before firing a right-footed strike into the bottom corner from the edge of the box.
Rubio Rubin and Jose Morales were denied by home goalkeeper Matt Freese before 18-year-old forward Olger Escobar gave Guatemala hope when he fired into the bottom corner with 10 minutes remaining.
But the US held on to give coach Mauricio Pochettino the chance to claim just the third major honour of his managerial career.
The seven-time winners had come into the tournament on a four-match losing streak, with Pochettino leaving out star player Christian Pulisic after the AC Milan forward offered to play in two friendlies before the Gold Cup, but wanted to be rested for the tournament itself.