"The confidence just continues to grow in our group," Matthews said. "Each game we've taken steps in the right direction of where we want to grow our game going into the quarterfinals. It's good to see."
Zach Werenski, Brock Faber and Tage Thompson also scored, Matthew Tkachuk and Jake Sanderson each had two assists, and Connor Hellebuyck made 23 saves for the Americans.
Tim Stutzle scored, and Maximilian Franzreb made 32 saves for Germany (1-0-2-0), which is the No. 6 seed and will play No. 11 Team France on Tuesday.
"A little devasted," Germany defenseman Moritz Seider said. "I think still there are plenty of positive things to take away. The starts have been great in all three games. That's something we've got to continue, but 20 minutes isn't enough to play with the big nations. If we play like that against France, I think we give ourselves a really good chance to advance. That's definitely something we've got to focus on."
Germany went 0-for-3 on the power play after going 0-for-4 in a 4-3 loss to Team Latvia on Saturday.
“I thought we hung in there pretty good, had stretches where we showed some offense, but at the end of the day, they’re lethal with the chances that you give them," Germany forward Nico Sturm said. "We’re going to analyze what we did wrong, but I think we’re going into the next round with a good feeling.”
As happy as Seider, Sturm and the Germans might have been with how they started, it was Matthews, the U.S. captain, who made sure the feeling didn't last heading into the first intermission.
He started his productive night with a cross-ice saucer pass to Werenski, who gave the Americans a 1-0 lead at 19:51 of the first period with a quick shot through Seider's legs.
"It's a great pass," Werenski said. "I knew he was going to make it. He's such a talented player. Not many guys would see that, but I saw him kind of shoulder check and see me, and a guy with his caliber, his talent is going to make that play. I was a beneficiary of it."