Canada began their IIHF Ice Hockey World Championship defence with a comfortable 4-1 victory over Czech Republic in Paris.
Ryan O'Reilly and Mike Matheson gave them a two-goal lead in the second period, but Czech Republic hit back in the third when Lukas Radil made the most of a powerplay.
Tyson Barrie restored the two-time defending champions' advantage and Jeff Skinner rounded off the scoring after the Czechs pulled goalkeeper Petr Mrazek.
In the other Group B match, Finland, silver medallists in 2016, got their campaign off to a winning start as Veli-Matti Savinainen's third-period effort clinched a 3-2 win against Belarus.
United States, like Canada, are not at their strongest with the competition coming at the end of the gruelling 82-game NHL regular season and their first outing ended in defeat.
A tripping penalty on Danny Dekeyser with the scores at 1-1 proved costly, with Patrick Hager making the most of Germany's extra man to snatch a 2-1 win.
There was plenty of drama in the opening match between Sweden and Russia in Cologne, with Sergei Andronov cancelling out Elias Lindholm's opener in the third period.
Overtime could not separate the sides but Artemi Panarin was the only player to convert in a shoot-out to clinch victory for Russia.