The Canadians started strong, but the U.S. took the lead in the 32nd minute and never trailed after that.
"The Americans were more physical today, but we were not consistent enough to win the game," said Canada head coach Francois Ratier.
Latoya Blackwood, Lisa Gauthier, Andrea Burk and Julianne Zussman scored tries for Canada while Andrea Burk had three conversions and Zussmann had one.
Jordan Gray, with two, Jane Parr, Sam Pankey and Jessica Wooden recorded tries for the Americans. Kimber Rozier tallied four conversions and a penalty.
"We had moments of amazing rugby and then we’d kind of fall back on defence," said Gauthier. "They saw the gaps and used the mistakes that we made. But when it was great it was great, we just have to build for the next game."
Canada was beaten 40-22 by the New Zealand Black Ferns on the first day of tournament play in Calgary while the Americans lost 39-13 to reigning World Cup champion England.
England lost 26-7 to New Zealand in Wednesday's other game.
The tournament wraps up Sunday in Edmonton when New Zealand plays the U.S. and Canada faces England in a rematch of the 2014 World Cup final.
"We definitely need to work on our defence, hitting low when we go into contact," said Gauthier. "We’re a little high so maybe bringing that down and doing just a little bit better than we did today will give us a good result Sunday."