In Finland only hardcore fans care about the tournament. Same applies to all junior tournaments in all sports. It just does not make sense to try to hype these kind of tournaments. Some games can be fun to watch but that's it.
Finnish media tries to spoonfeed this tournament to people in sport news, but it doesn't help because games are not shown on free channels. That's why people watching sports know that the tournament is ongoing, but they watch just the highlights from sport news. When Finland got to final last year the final game (SWE-FIN) was shown on free channels and it got good ratings, but still nothing like WHC games when Team Finland is playing.
One reason why Europeans see this tournament differently is that the best European U20 players already play in professional leagues with men. It's much more interesting to see how they fare against men than to watch how some top U20 players dominate against some kids who will never make even the top Euro leagues. Example: in 2005 Finland had star players like: Hokkanen, Honkaheimo, Korhonen, Kuukka, Mäntymaa, Tieranta, Kolehmainen, Makkonen, Nurmi, Seitsonen, Tukonen, Riska, Piispanen, Nabb, Marjamäki.... There were a couple of future NHLers, few KHLers, but most of them haven't made formidable career even in Finnish Liiga.
Most Canadian U20 players play still in juniors and that's why this kind of junior tournament fits that stage of career quite well. In Europe you play in juniors basically only if you're not good enough to play with men, and that's why junior hockey is not highly regarded. Even Puljujärvi plays with men in semi-pro league even though he's only 16 years old.
Edit. it's a bit ironic that NHL promotes this tournament unlike WHC. Still NHL teams don't want to let players to tournament any more than to Olympics, for example. NHL just tries to get the benefits, but holds all the players who are useful enough to play in NHL. That's typical NHL behavior. Other pro leagues release the players, even though many of the players are very important for their teams. Yeah, NHL is bigger business, but relatively the impacts are the same.
Actually the impacts in Europe can be bigger. In SHL a team can ultimately be relegated because some player played in WJC (let alone got injured). In NHL worst that can happen is that team finished last and gets advantage in next draft.