penalties for fighting are 5 minute majors. They serve all 5 minutes in the penalty box, both fighters, penalty isn't shortened if a goal is stored. Teams don't play shorthanded, so it was 5 v 5.
2nd fight in USA v Canada was started with a cross check minor penalty on JT Miller, so Kyle Conner for the US served that 2 minute penalty for the US since Miller was in box for 5 for the subsequent fight. Canada had a 5 on 4 penalty play, but Canada had 3 guys in the box for 5 minutes and the US had 3 in the box for 5 minutes and the US had 1 in the box for 2 minutes or until Canada scored a goal, which they didn't.