Poor WJC performance 'can' be an indication of future struggles like great NCAA/CHL performance 'can' be an indication of future success. Not sure what your point is beyond that.
Also not sure what you mean by 'perform', but he wasn't good statistically or by the actual eye test. And the excuse of chemistry doesn't hold much water, he played with Schmaltz most the tournament. He just wasn't very good at that level of play in that tournament.
I haven't caught any Sioux games recently, but the stat sheet makes it look like he's expectedly cooled off a bit?
We're talking about a 7 game tournament in a different environment for the players. A different system can also be a factor. 7 games (at most) is not that much of a sample size. It's nice if your prospects are doing good at the WJC, but in the end i wouldn't say it's that important. As a swede i remember Max Friberg a couple of years ago. He scored some crazy clutch goals that tournament again and again and was the topscorer with 9 goals in 6 games. Also had the 2nd most amount of points (after Kuznetsov who had 2 points more with 1 extra game). Now he's struggling big time in the AHL and that WJC tournament is basically going to be the highlight of his career (not a bad highlight, but still). Max was never considered a top prospect, and even after that tournament the odds might have been against him making it. Still, he were able to dominate against "the best players/prospects in junior", no one was better than him that tournament.
Matthews carried the US big time last year. Ron Wilson heavily relied upon his line, while the 2nd line also got some minutes. 3rd (Boesers line for the most part) and the 4th line barely got any minutes at all. Boeser had the opportunity with Matthews when DeBrincat went down. He didn't take the opportunity, he looked a little bit lost indeed. That was basically his chance in the tournament. Worth mentioning is that he never got any PP minutes as far as i know (even when he played on the 1st line). Schmaltz got those minutes though, and if i had to guess, i'd say that's were he got most of his points in the tournament as well.
I think a lot of the players on that US team weren't good enough, or at least didn't stand out even "if the stats says otherwise". Matthews dominated, Tkachuk did his job with Matthews, White filled in pretty good on that line in the end. Werenski was great, as was Nedeljkovic who was possibly the best goaltender in the tournament (i'd say Söderström though.) I have probably missed someone who was great. But for instance i didn't think the 2nd line was that good, they had their moments but overall they were nowhere near as good as the Matthews line. I wonder how many points that line had before the blowout game against Sweden which was just a gutless performance by the swedes just like the year before in the bronze-game.
He has been in a little bit of a slump as far as i know the last 4 games, yes. He should come around though, he started of the year extremely strong.