"And, of course, Antero Niittymaki was very good when we had difficult times."
Yan Stastny missed a penalty shot for the US just 2:21 into the game after Mikko Luoma hooked the American forward, who broke away alone in front of the Finnish net.
Finland, which has 10 players returning from the squad that lost the Olympic final to Sweden, took the lead midway through the first period when Mikko Koivu knocked a rebound past American goalie Craig Anderson.
Anderson, who had the best goals-against-average and top save percentage in the tournament going into the game, gave up another goal early in the second period when Sean Bergenheim beat him with a shot between the pads.
Petteri Nummelin added a power-play goal halfway through the session, beating Anderson with a wrister to the stick side.
Lasse Kukkonen finished scoring with less than six minutes left of the game.
Michael Nylander, Jonas Nordquist, Magnus Johansson and Per Hallberg scored for Sweden, which also remained unbeaten.
Russia, which was idle, tops Group F with six points. Sweden has five, Switzerland four and Belarus two.
Belarus forward Sergei Zadelenov ended Swedish goalie Johan Holmquist's shutout bid at 9:14 of the third period, intercepting a poor clearance pass by Sweden's Mattias Timander and beating Holmquist with a wrist shot.
Sweden outshot Belarus 42-23, and Belarus coach Glen Hanlon said the game reflected why Sweden was rated first and Belarus ranked 12th in the International Ice Hockey Federation's world rankings.
"They were the bigger faster hockey team and the world champion and we were definitely sitting back waiting to see what would happen," Hanlon said. "After we kind of relaxed and got into it a little bit we played a little bit better."
Forward Henrik Zetterberg said his team was looking forward to playing some of the tournament's other stalwarts, like Canada and Russia.
"I think we're confident. It's going to be fun to play a little different style of hockey and to play a little better teams," Zetterberg said.
Like many of the teams at the World championship, Sweden brought a younger lineup than it has in past years.
Switzerland also kept its unbeaten run, tying Slovakia 2-2 when forward Sandy Jeannin scored with 1:56 left in the game.
The Czech Republic rallied to beat Norway 3-1 on goals by Jan Hlavac, Jaroslav Balastik and Petr Tenkrat after Morten Ask had opened the scoring on a power-play.
In the relegation pool, Italy beat Kazakhstan 3-2 and Slovenia drew 3-3 with Denmark.