Cooper opened the scoring in the 3rd minute after robbing goalkeeper Mexico goalkeeper Celeste Espino following a back pass. The Duke striker finished with a tournament-leading eight goals. Talia DellaPeruta scored on a 43rd minute penalty kick after Alexxandra Ramirez fouled Alyssa Thompson.
The USA had a 12-10 edge in shots over Mexico, which forced three saves from goalkeeper Neeku Purcell, more than required by U.S. goalkeepers in the previous six games.
Coach Tracey Kevins' team's 49 goals (while conceding zero) broke the tournament record of 40 goals the USA managed two years ago, when it beat Mexico, 4-1, in the final.
Both the USA and Mexico qualified for the 2022 Women's U-20 World Cup as semifinal winners, while Canada qualified thanks to its 2-0 win over Puerto Rico in the third-place game.
March 12 in Santo Domingo
USA 2 Mexico 0 (Cooper 3, DellaPeruta (pen.) 43.
USA -- Purcell; Rouse, Mason, Reale, Guidry; DellaPeruta, Moultrie (Colton, 62), Missimo (Flynn, 78); Thompson, Cooper, Jackson Byars, 62).
Mexico -- Espino; Monroy, Gutierrez, Guzman, Lopez, Ramirez; Delgado, Vazquez (Maldonado, 46), Avilez; Mauleon, Villanueva (Flores, 80).
Referee: Marianela Araya (Costa Rica)