After the two teams could not be separated after 120 minutes, Brazil eventually eliminated Mexico on penalties as they go for gold.
Miles Robinson headed in the 118th-minute winner as the United States won another title after June's CONCACAF Nations League success.
Mexico missed a second-half penalty before Hector Herrera netted late to keep their bid for a 12th Gold Cup alive.
Substitute Hirving Lozano's brace lifted Mexico to a 2-1 friendly win over Iceland in Texas.
After the two teams could not be separated after 120 minutes, Brazil eventually eliminated Mexico on penalties as they go for gold.
Miles Robinson headed in the 118th-minute winner as the United States won another title after June's CONCACAF Nations League success.
Mexico missed a second-half penalty before Hector Herrera netted late to keep their bid for a 12th Gold Cup alive.
Substitute Hirving Lozano's brace lifted Mexico to a 2-1 friendly win over Iceland in Texas.