Cristian Savani led the Italians with 19 points in a 28-26, 25-20, 25-20 victory.
The American men lost only one set in their first four group games, including a victory over the Brazilian side they defeated for the gold medal at the 2008 Olympics.
After jumping to a 2-0 lead against Russia in its final group game, the United States did not win another set in the tournament. The Russians came back to win three sets in a row in capturing that match, and the Italians dominated the Americans in the quarterfinals.
Brazil defeated Argentina in three sets to open quarterfinal play Wednesday and will meet Italy in the semifinals.
The other semifinal will bring together Bulgaria and Russia after they advanced in three sets.
Russia eliminated Poland and Bulgaria defeated Germany in their quarterfinal contests.
Swim Week Miami Beach 2014 [PHOTOS]