While the NHL short run revenues would jump by moving a few low-revenue US teams to hockey-mad Canada, I would be careful of turning hockey into a 'Canadian game played by crazy Canucks' even more than it already is in the US. The US is a much bigger market and I think that if the game can gain more traction in some locations, it would eventually be a net positive for the league. Most Americans can't locate Calgary on the map, so how excited can they get for a Calgary-US team game?
Don't forget more Canadian teams might cannabolize some of the existing Canadian profits (not by much though IMO).
I'm not convinced that people who don't support you're product are more important than people who are responsible for your operating expenses, profits and financing outlets in regions where people don't support your product.
Canadian Tire didn't well one time when they expanded into Texas IIRC but they hold their own quite well against competition from our friendly southern elephant here in Canada.
I think expansion into the US is too rapid leading to greater opportunity for negative exposure than simply conquering a market or two at a time as opportunity presents. LA (California) was won. Florida was an obvious goal but saturating a market and changing the product to win them over has accomplished nothing except to PO the people who support your product and hurt profits. Not to mention negative exposure for the sport and the people who created the game.