Canada's Olympic campaign was delayed as their opening match was postponed but they showed little rustiness by finishing off a gallant Swiss side with three goals in the final period.
After a scoreless opening period in which Switzerland were outshot 17-2, Canada took the lead with a Natalie Spooner power play goal in the eighth minute of the second period.
Switzerland had two players sent to the penalty box in quick succession early in the final period, and Canada made the second power play count with Sarah Fillier doubling their lead.
With less than seven minutes remaining, Julia Gosling tipped one in to beat Swiss keeper Saskia Maurer who had otherwise impressed by stopping 51 shots but she conceded again to Daryl Watts as the Canadians wrapped up the win in style.
The US strolled to the Group A win against a Finland side who were playing their first game following Thursday's postponed clash with Canada after four Finnish players tested positive for norovirus, and other members of the team isolated as a precaution.
"We're happy that now we have a full team again and we are ready to start building from this game," Finland forward Emma Nuutinen told reporters.
"We're definitely not happy with the result, but we also know that this was a rough start for our Olympic journey."
JD Vance in the stands
US Vice President JD Vance, who was booed during Friday's opening ceremony, slipped into the stands at the Milano Rho Arena during the first intermission, attending his second US women's hockey game of the tournament and was later joined by influencer-turned-boxer Jake Paul.
Alex Carpenter opened the scoring with a power play goal in the 16th minute and Taylor Heise and Megan Keller netted in quick succession early in the second period.
Hilary Knight tied the American women's all-time record for Winter Games goals, scoring her 14th overall halfway through the second period on a power play and Abbey Murphy scored her first Olympic goal late on as the Americans eased to their second win.
Canada will begin their title defence against Switzerland in Group A's other game, despite a positive norovirus case reported on the Swiss team.
All five sides from Group A will advance to the quarter-finals, where their seedings will depend on the final placings in the preliminary round.
Germany and Sweden win in Group B
In Group B, Germany scored 44 seconds into their 5-2 win over Japan when forward Luisa Welcke rifled the puck toward the goal and captain Daria Gleissner tapped in the rebound from close range at Milano Rho Arena in the Group B match.
Forward Emily Nix put Germany 2-0 up in the ninth minute when she slipped through the Japanese defence and flipped an easy wrist shot around goalie Miyuu Masuhara and Nicola Hadraschek shot it through the five-hole less than five minutes later.
Germany kept their foot on the gas in the second period, when Hadraschek's point shot ricocheted off Masuhara's chest and into the goal in the sixth minute and alternate captain Laura Kluge hit one in off the crossbar about five minutes later.
Japan injected life into the game with two goals in 22 seconds late in the second period, courtesy of forwards Mei Miura and Yumeka Wajima, but German goalkeeper Sandra Abstreiter stopped the Japanese momentum in the final period.
Japan will hope to tune out the home fans as they next play Italy on Monday when Germany face France.
Italy had opened with a 4-1 win over France on Thursday but were brought back down to earth at the Santagiulia Arena in a 6-1 defeat by the Swedes who made it two wins from two following a 4-1 victory over Germany.
Jessica Adolfsson put Sweden ahead in the 10th minute, Sofia Lundin doubled their lead 10 minutes into the second period and Sara Hjalmarsson added a third two minutes later.
Franziska Stocker pulled one back for the Italians six minutes before the end of the second period but Sweden restored their three-goal cushion just over a minute later through Hanna Olsson.
Thea Johansson netted twice in the third period to round out the win and Sweden can clinch their place in the last eight with victory over France on Sunday.
The top three in Group B make the quarter-finals.
