Shortstop Christian Arroyo was the tournament's most valuable player as the U.S. won the U18 title for the first time since 1999.
Team USA scored three times in the third to take a 4-1 lead. Jeremy Martinez had an RBI single and scored on Chris Okey's base hit.
Gareth Morgan and Josh Naylor each drove in a run for Canada, which had its best finish in the tournament since it won gold in 1991.
Left-hander Ian Clarkin pitched six effective innings for the U.S., yielding two runs and four hits.
The American team was managed by Scott Brosius, who played 11 years in the majors with the Athletics and Yankees.