I think the author has a valid point. 1/3 of the MLB players are foreigners, about 1/2 the NHL is foreign, increasingly the foreigners are playing in the NBA.
I see the kids today and they are nice, but they don't have the competitive desire of yesteryear.
300 million people in the United States vs. 6 billion in the entire world. What other nation offers anything close to the NHL, NBA, MLB, NFL. Not only do we have the epitome of professional sports (except soccer), But as a nation allow others to immigrate to our country, if they so desire, or not, and to work in our industry (sports). In other words, we have something to offer, and we allow others to play. Its only natural that in a nation that makes up only 5% of the worlds population, that when we open our doors to people of other nations, to play in "our" sports, on "our" teams, that those teams really wouldn't reflect "us" as much as the rest of the world. And thusly, the US wouldn't appear to be so dominating.
But in the end what has really happened, is not the the US has gotten worse, and the rest of the world has gotten better. But the US has actually given the rest of the world better equipment, better training, better coaches, better sports phsycology, better sports medicine, better experience, and a better goal or aspiration, all to motivate them beyond where they were or even where they are.
A rising tide floats all boats.