The article is right about talent dilution at the time teams are added, but incorrect over a longer period of time. If two new teams are added, assuming a 22 man roster, that's 44 new jobs at the NHL level that must be filled by players who did not make the cut before expansion. However 3+ years out, as more players are absorbed into the NHL-level of play, simply having the exposure should increase talent levels.
There were several reasons why more European players weren't in the older NHL. There was something called the Iron Curtain for starters, so that had some effect on Russian, Czech, Slovak. Belarus, Latvian, Lithuanian, East German, Kazakhstan, etc. (did I get most of them) players' options. If there were only 12 NHL teams, for example, and all twelve were sufficiently staffed by North Americans, why would teams spend the money to scout and recruit overseas? We are talking about significant sums of money. Some of you older folk here have no excuses either in forgetting how difficult it was to communicate and transmit large amounts of data even in the 1980's. At least by then, you could direct dial overseas! Internet? Yeah, right.
I guess the point is that there were other factors as to why the proportion of players from various countries changed in the past 20 years, including custom/tradition, and the lack of a global perspective in major league North American sports then vs. now. Certainly expansion was a factor as more jobs became available, but the fact that non-North American players were being recognized as having a sufficient level of talent to be considered (thanks in part to the Summit Series and related international competitions that let the new countries exhibit their talent). It was a bit of a cottage industry. As demand for talent grew, new sources had to be found. The world was getting smaller too thanks to greater travel and communication possibilities, and more players were willing and able to change addresses.