South Korea finished the tournament with a 6-2 record, while the U.S. was 5-3.
Japan beat Mexico, 11-1, in the bronze-medal game.
Byung Ho Park hit a three-run homer as part of a five-run fourth inning to all but clinch the gold medal. Hyun-soo Kim led the South Korean attack by going 3-for-5 with three RBIs, and he also earned tournament Most Valuable Player honors. Keunwoo Jeong also went 3-for-5 and drove in a run.
South Korea starter Kwang-hyun Kim fanned five over five shutout innings, while four South Korean relievers combined to hold the U.S. to just three baserunners over the final four innings
Marlins farmhand Elliot Soto was the lone American to post a multihit game, while Zack Segovia allowed two runs in two innings to take the loss.
Cash Kruth is a reporter for MLB.com. Follow him on Twitter at @cashkruth. This story was not subject to the approval of Major League Baseball or its clubs.