Brazil's men's team defeated Venezuela, 90-88, to finish fifth and Argentina beat Uruguay, 71-64, to finish seventh.
The U.S. team, which lost to Puerto Rico, 73-68, Thursday, will meet Cuba today for the bronze medal.
Puerto Rico plays Mexico in the championship game.
Edgar Ruiz of Mexico advanced to the 139-pound title fight against Steve Johnson of Colorado Springs, Colo., by winning a semifinal bout against Anibal Acevedo of Puerto Rico, who was disqualified for a low blow.
Johnson advanced to the gold medal bout when Luis DaSilva of Brazil forfeited because of a broken finger.
Referee Gustovo Campos of Uruguay stopped the Ruiz fight midway through the second round when Ruiz doubled up on the canvas and Campos counted him out. But Campos reversed himself and disqualified the Puerto Rican for the low blow.
The U.S. team won the bronze medal by defeating Cuba, 4-0.
The Americans finished with a 3-2 record.
Argentina won the gold medal with a 5-3 victory over Brazil.
Tony Muse of West Des Moines, Iowa, who had won the 300-meter sprint earlier in the games, took the golf medal in the 5,000 in 8 minutes 36.54 seconds. Muse's brother, Dante, earned the silver medal in 8:36.76.
The U.S. women's team took the bronze in the 5,000 relay in 8:19.62. Argentina won the gold medal in 8:19.03 and Colombia finished second in 8:19.30.
Rosa Sastre of Argentina took the gold medal in the women's 3,000 in 5:42.52. Dani Lewis of Lacey, Wash., finished fourth in 5:43.12. Deanna Parker of Des Moines, Iowa, was seventh in 5:45.84.
Cuba's Nelson Saenz won the gold medal at 83 kilograms by defeating Lucio Fleitas of Brazil, 2-0.
Venezuela's Arlindo Gouveia beat Augustin Ayala of Mexico for the gold at 54 kilograms.