Despite the U.S. taking over the stat sheet for the first period, Finland's constant pressure in the offensive zone kept them on their heels through, getting good looks left and right but ultimately failing to convert on most of them.
Finland's Henri Jokiharju (25) scored the first goal of the game just over seven minutes into the first period.
But the U.S.'s own Brady Tkachuk responded with a goal of his own to tie it up 1-1 before heading into the end of the first period tied up.
Both teams failed on their lone power play opportunities but both goaltenders in Juuse Saros (Finland) and Connor Hellebuyck both made a handful of crucial saves.
Brock Nelson (U.S.) almost put a laser past Saros in the first period but it ringed off the pie.
Second Period
Finland started off the second period controlling the moment and getting off more shots than the U.S. But the U.S. failed to take advantage of an early power play making it 0-2 on the night at this point.
They almost found the net but Saros was a brick wall for Finland making great save after great save. Unfortunately for Finland, the U.S. managed to find the net to go up 2-1 in the second off a beautiful redirection by Matthew Boldy.
The period saw a couple of scruffles with, of course, Brady Tkachuk at the heart of both of them. But Finland committed a horrendous hooking penalty with just 2.2 seconds left before heading into the third, giving the U.S. a perfect opportunity to take a two-goal lead.
Third Period - the flood gates opened
The USA opened the floodgates to start the third period with three goals in three minutes off of four shots, with the first coming from Matthew Tkachuk within the first 15 seconds on the power play that carried over from the second period.
Then, just 15 seconds later, Jake Guentzel scored his first goal of the tournament to give Team USA the 4-1 lead.
Then, of course, Matthew's brother Brady scored his second goal of the game to put the USA up 5-1.
And who else but to score the sixth and final goal of the game for Team USA other than Brady?
Team USA flat-out dominated in the third period with Finland completely gassed. After USA head coach Mike Sullivan put the Tkachuk brothers on the same line with Jack Eichel, Finland never had an answer, proving to be the most dominant line of the first games of the 4 Nations.
Finland deserves credit for their play up until the late second period. But the costly penalty at the end of the second period ending up proving to be a critical mistake.
The USA outshot Finland 32-21 and out-hit them 32-16 for the game.
4 Nations standings and schedule
Finland will square off against Sweden at 1 p.m. eastern time while Canada and the USA will have a puck drop at 8 p.m.
The current standings for the 4 Nations are as follows:
USA: 3 points
Canada: 2 points (overtime win)
Sweden: 1 point (overtime loss)
Finland: 0 points