MONTREAL — Mike Tyson once mused that everyone has a plan until they get punched in the face.

Well, Team USA’s plan was to punch ’em in the face.

Embracing the villain role in Canada, Matthew Tkachuk told younger brother Brady he wanted a piece of Brandon Hagel as soon as he saw his cross-state, cross-country rival’s name on the lineup card.

Then he asked Hagel, who obliged in a snap. A lit fuse right from the drop of the puck.

“I wasn’t saying no,” Hagel said of the fight. “Listen, I don’t think he was expecting what he got from me.

“I’m not backing down. I mean, a little bit of the talk was, these guys are going to take over the Canadian way. But I’m not gonna let it happen.”

Human nailgun Sam Bennett hopped the boards for the following draw and shed gloves with Brady.

The next shift, Colton Parayko and J.T. Miller threw down.

Yes, the long-awaited Canada–U.S. showdown began with two fights in three seconds, and three scraps in first nine seconds.

“The message we wanted to send is: It’s our time. We’re in a hostile environment, and we wanted to show that we’re not backing down,” Matthew Tkachuk said, following Saturday’s 3-1 win for the Americans that secured their birth in the 4 Nations Face-Off final.

“It’s just a group of guys that are fired up to play their biggest rivals in this type of environment, so we had an absolute blast from the start.”

Truth be told, we all did.

It was nasty and political, loud and mean, nerve-wracking and exhilarating.

“An adrenalin rush,” Brady Tkachuk said.

High-end skill matched with hard-nosed defence. All-world goals and bone-crushing hits, 31 of them delivered in a tone-setting, hair-on-fire first period.

Charlie McAvoy dumped Connor McDavid on his keister twice with vigour. McDavid streaked in for one of the prettiest backhand roof jobs Connor Hellebuyck will ever surrender. And Miller swung an upper-cut so hard at Parayko, he punched his own helmet off.

Even though Canada lost — thus thrusting a final berth in doubt — coach Jon Cooper believes the first minute of Saturday’s game exceeded the electricity of the first minute of Wednesday’s win over Sweden, when Canada’s power-] play clicked in a flash.

“You know why it topped it? Because it wasn’t planned. That wasn’t two coaches throwing guys over saying, ‘This is happening.’ None of that. That was as organic as it gets,” Cooper said.

“It’s probably 10 years of no international hockey exhaled a minute and a half.”

Added U.S. coach Mike Sullivan: “I just think it’s very indicative of what this means to the players. There’s two teams out there that are very competitive, that have a ton of pride for their respective teams and countries. For me, when you have an investment in trying to win like the way that it occurred, I think (the fights) an indication of it. What an incredible hockey game.”

The ridiculous absence of country-versus-country competition for this era of NHLer (a shame both the league and players must own) helped shake the Coke bottle.

So, too, did the dual response to the pre-fight anthems, which, fittingly were sung after Georges St-Pierre introduced the home team and riled the masses.

“The Star-Spangled Banner” was booed lustily tip to tail by Canadians fed up with President Donald Trump’s threats to annex.

“O Canada” was blared at full throat by the 21,105 lucky enough to catch some fights before a hockey game broke out.

Did the anthem booing trigger the Tkachuks to chuck knucks?

“No. No,” Matthew said. “That’s called me, Brady and Millsy in a group chat during the day.”

When it was all over, the Americans were blaring Aerosmith’s “Dream On” in the visitors’ room, and Canada’s fell into a quiet resolve.

But all-stars on both sides described the event as one of the best and most intense games they ever played in.

As powerful as playing in a Stanley Cup Final?

“It’s close, if not right there with it,” McDavid said. “The emotions, the fans, obviously the energy in the building, the rivalry. It was special to be a part of. Fun night.”

That goes for the tension erupting with excellent hockey, and for a few face punches.

Cooper was asked if fighting belongs in an international showcase like this?

“I didn’t see anybody running for the exits,” he replied.

Canada must now run to the drawing board, with a must-win versus Finland looming in 36 hours in Boston.

Lines should be tweaked. A goalie might get swapped. And health will be hoped for.

The strategic portion, Cooper assures, will be taken care of by the coaches.

“It doesn’t work unless you have a team that cares — and that test we passed. We have a team that cares. The result is unfortune, but I don’t think anybody can leave that building and say that didn’t that team didn’t stick up for each other, care for each other, and play with passion. And when you do have that, the ceiling is limitless,” Cooper said.

“This is our Game 7.”

• Cale Makar — Canada’s best defenceman ad top minute-muncher — was close to playing Saturday.

“Those decisions are made for the benefit of the player,” Cooper said. “Trust me, he’s the one that wants to do it the most.”

Canada is hopeful Makar can go Monday in Boston.

Considering the difficult circumstances — flying away from vacation and not even skating with Team Canada until warmups — emergency recall Thomas Harley didn’t look out of place at all.

“That’s tough, right in the middle of the tournament, whole new group of guys, didn’t (practise) the system work,” Parayko said. “So unreal game by him. Just incredible.”

Did you expect the start like that? “I expected an intense start, for sure, an emotional one, or however you want to put it. But, I mean, I don’t know if you really expect three fights or whatever. But yeah, you definitely expect an intense start.”

• Cooper refused to blame Jordan Binnington (.909) — who was outdueled by a zoned-in Connor Hellebuyck (.962) — for the loss. But he didn’t give his goalie a ringing endorsement either.

Binnington wants both goals he allowed back.

A compelling decision awaits Canada’s crease.

Binnington has warmed to the pace of the tournament.

If Canada goes with backup Adin Hill for the must-win, the Vegas Golden Knights goalie will have waited 11 days between starts.

• A banged-up Matthew Tkachuk was limited to just 11 minutes and 10 seconds of action and told the trainers in the third period he was too hurt to play.

Post-game, however, he said there is “no concern at all” over his lower-body injury — despite needed further evaluation from doctors.

“Other than Game 7 last year, this has been the highlight of my hockey career,” Tkachuk said. “I’m just going to enjoy it with the guys. We have such a fun group in there, and it’s going to be a fun plane ride tonight. Lots of laughs. We’re having a lot of fun.”

• Drew Doughty was Canada’s most improved player.

Only McDavid and Josh Morrissey saw more ice than the veteran (21:15), who pitched in on both special teams and sprung McDavid for his goal-scoring break with a perfect stretch pass.

• Game-winning goal scorer Dylan Larkin says he’ll tell his grandkids about this night. He’s 28.

“That was one of the best experiences of my life,” Larkin says. “Just an unbelievable hockey game. I hope you guys feel the same way.”