Former Major Leaguer Terry Tiffee, who played for the Phillies' Triple-A club this season, hit his fourth home run of the tournament, pushing the U.S. winning streak to 12 games since a tourney-opening loss to Venezuela.
The U.S. (6-0 in the third round) already has earned the right to play for the gold, and will face The Netherlands on Friday before taking to the field again Sunday for the title.
Cuba (4-2) could lock up a place in the gold-medal game with a win over Canada Friday.
If Team USA wins the tournament, it would mark America's first back-to-back World Cup victories since 1973-74. The U.S. stopped a string of nine consecutive titles for Cuba in 2007.
If Cuba advances to face Team USA, it will be the seventh time the countries have played in the World Cup final, with Cuba holding a 6-1 advantage.
In Thursday's game in pool play, Team USA took a 4-0 lead on an Ike Davis RBI, Tiffee's two-run homer and a Jason Castro RBI single. Lucas Harrell earned the win, allowing only one hit over four innings after relieving Trevor Reckling, removed after one inning due to injury. Ehren Wasserman picked up the save, giving up one hit in 2 1/3 innings.
In other World Cup games, Venezuela beat Australia, 9-4, Canada beat the Netherlands, 11-5 and Puerto Rico defeated Chinese Taipei, 8-2.
John Schlegel is a national reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.