Dempsey added two more in the second half to give him a tournament-leading six goals.
“That’s always great to do but you can’t do it without your team mates,” Dempsey told reporters of his hat-trick. “Today we came out and played well and finished our chances. As a team we’re getting better as it goes along.”
The Americans had delivered patchy performances in their three group matches, where they recorded two wins and a draw, but they were ruthless against a Cuba side that had scored just one goal in three games.
Gyasi Zardes, Aron Johannsson and Omar Gonzalez also scored for the United States, who next face Jamaica for a place in their sixth straight Gold Cup final.
Jamaica overcame the absence of suspended forwards Darren Mattocks and Je-Vaughn Watson to advance to the semi-finals with a 1-0 win over Haiti also on Saturday, Giles Barnes scoring the winner in the seventh minute.
Jamaica, who are trying to reach the final for the first time, play the United States in Atlanta on Wednesday.
(Writing by Jahmal Corner in Los Angeles; Editing by Peter Rutherford)
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