It's definitely not easy.
I get just as angry about "game management" and "equalizing calls" which happens in the NHL a lot.
You'll be down 5-1 thanks to 3 PP goals, and they hand you 2 PPs in the last 5 minutes of the game which amount to nothing so as to try and compensate. First of all, teams don't commit infractions evenly. Secondly, the timing of a call can be as critical as the call itself.
If my team has had one or two more PPs over the other team, and then we score to go up 2-0, I just count the shifts for the make-up call to come our way. Reffing the score is a real thing.
NHL refs do fairly well on high-sticks and hooks, slashing to the hands. They do far worse on charging, boarding, cross-checking, interference and tripping, which are often seemingly arbitrary and handed out depending on what's happening in the game.
So, that being said, when I watch IIHF tournaments, I see plays that in no universe I'm familiar with get called for penalties, which rarely happens in my mind in the NHL. Plays that I just cannot comprehend the thought pattern behind the call. Where a guy loses his footing with no one around and a penalty gets called. I think the difference is that the mistakes at the IIHF level are so glaring that they are often beyond belief. Like "what the hell are they possibly thinking?" type of calls.