Zach Parise scored midway through the second period, adding to first-period goals by James van Riemsdyk, Dustin Brown and David Backes, and giving the United States a 4-1 lead over the Czech Republic at the second intermission.
Meanwhile, Canada and Latvia went scoreless in the second period and remained tied at 1.
The games are being played concurrently, and the winners will face off Friday with a spot in the gold-medal game on the line. Finland, following its 3-1 win against host Russia, and Sweden play in the other semifinal.
Parise’s goal came on the power play, the only one of the game so far; The U.S. has spent just 1 minute 33 seconds with the advantage. Ryan Suter had an assist, his third of the game, on the goal.
Meantime, Jonathan Quick has stopped 12 of 13 shots on goal through two periods.
Canada on the other hand, has peppered Latvia with shots on net, 35 to 11 through two. But only Patrick Sharp’s goal at 13:37 of the first has slipped past Lativian goalie Kristers Gudlevskis.
More Olympic hockey news:
Analysis: Why Russia went out with a whimper
D.C. Sports Bog: Milbury and Roenick rip Ovechkin