The U.S. put up four runs in both the first and third innings and held Canada scoreless, allowing them to pick up the victory in five innings.
Despite the lopsided final score, Canada did threaten in the top of the first inning, as Melanie Matthews of Surrey, B.C., led the game off with a single and moved to second on a single by Jenn Yee of North Delta, B.C.
However, the next two batters struck out to end the threat. In the bottom half of the inning, the United States struck for four runs, highlighted by an RBI single by Kaitlin Cochran and a three-run home run off the bat of Stacy May-Johnson.
In the second inning, Toronto's Joey Lye hit a two-out single and advanced to second on a wild pitch, but could not advance any further.
The following inning, Matthews smashed a leadoff double and was immediately sacrificed to third by Toronto's Victoria Hayward, but Canada was unable to bring her into score.
American Valerie Arioto hit an RBI single in the bottom half of the inning, followed by a three-run home run by Samantha Fischer, giving the US a big 8-0 lead.
After Canada was retired in order, the United States added another run on a sacrifice fly, and shut down the Canadian offence in the top of the fifth to win the game on the run-ahead rule.
Pitcher Marina Demore of Richmond, B.C., took the loss, allowing seven runs on seven hits and a walk and a strikeout in two innings and a third pitched. Edmonton's Karissa Hovinga threw an inning and two thirds of relief, allowing two runs on five hits with a strikeout.
Canada will end its round-robin schedule with a doubleheader on Sunday night, taking on Puerto Rico (0-4) followed by Brazil.
The United States lead the standings with a 4-0 record, while Australia and the Netherlands both have a 3-1 record.