Here’s a number: 8 million.

That’s how many American kids are playing soccer, according to the 2009 Census. They’re playing in backyards, at school, on manicured suburban fields, on crowded city streets, in the heat of summer, in the cold of winter.

Even more than that are watching. More Americans than ever before have been watching the U.S. men’s national team compete in this World Cup. They watched to see if the team could exact revenge against Ghana (yes), if it could compete with Portugal (yes), and they’ll watch to see if the U.S. can beat the mighty Germans (we’ll see).

Click here for more on the 2014 World Cup.

It’s easy to fall into sermonizing and hyperbole during a World Cup, but one thing can’t be overstated: The 8 million kids watching this tournament, watching this team, are witnessing something very important to the evolution of the game in the United States. They are seeing the future. Those kids are seeing that they can become professional players, and that they have more opportunity than ever to play the game at the highest level.

Underneath all the good cheer and enthusiasm for the sport in the States, there is a debate raging about where and how young American players should train to become professionals: at home or abroad?

On one side is Major League Soccer and U.S. Soccer, which are investing millions into training American players. On the other is Jurgen Klinsmann, who is emphatic that the best Americans should learn their craft in the best leagues of Europe.

U.S. Soccer’s Development Academy, established in 2007, now has about 80 teams — approximately 3,700 kids. All 16 American MLS clubs have an Academy team. Those clubs are investing millions of dollars into those development squads. They provide free training and access to the same facilities where MLS players work. And they’re retaining the very best through the Homegrown Player Rule.

But all those kids, those 3,700 kids, are hearing the coach of their national team tell them to forget their homeschooling and do a semester abroad, as it were. “The more players we can get playing at the top levels [in Europe], the better it will be,” Klinsmann told The New York Times Magazine. In the same article, he derided Landon Donovan’s 2013 comeback by saying, “He came back, and he was playing in MLS, and people say, ‘Oh, he’s playing well,’ but what does that really mean? This is where MLS hurts him. He was playing at 70 percent, 80 percent, and he was still dominant. That doesn’t help anyone.”

Interestingly, while Klinsmann has been urging his American charges to learn their trade in Europe, they haven’t been answering that call.

Check out these numbers:

• 19 American-born players on the USMNT
• 15 American-born players on the USMNT who play or played in MLS
• 10 American-born players on the USMNT who are currently playing in MLS
• 11 American-born players on the USMNT who played college soccer

MLS and NCAA soccer continue to be the primary developing grounds for American talent.

And we’re seeing those American-bred players succeed.

Matt Besler emerged from the Kansas plains and has become the USMNT’s most reliable defender. Graham Zusi emerged from Matt Besler’s basement to become a talented, box-to-box midfielder. Kyle Beckerman put in 14 years in MLS before playing in a World Cup, and he’s been a rock in the midfield. DeAndre Yedlin came up through Seattle’s Development Academy, signed a Homegrown Player contract, and, at the age of 20, created the go-ahead goal against Portugal on Sunday.

This winter, I wrote a story on Matt Besler and Omar Gonzalez for ESPN The Magazine. During one of our conversations, Besler said to me, “In the future, the goal of the MLS should be to try and have as many national team players as possible playing in America. You see that with Italy. You have almost nine out of 10 guys on the national team playing in Italy.”

OK, so Italy just got knocked out of the World Cup. But you get his point: For the top European national teams — Spain, Germany, Italy, Netherlands — the majority of their national team players compete in their domestic leagues. Spain’s conquest of the 2008 and 2012 Euros and 2010 World Cup was a direct outgrowth of the work Barcelona did to develop players. Klinsmann has talked continuously about developing an American style of play, yet he has derided the place where that style would develop.

So, how will this all play out? We’re about to see. Tomorrow the United States plays Germany. Our German head coach, who won a World Cup with Germany and nearly coached the nation to another, now with his team of American and German American players, is going to play … Germany. The U.S. is playing for its fate in this World Cup.

But it’s playing for more than that. It’s playing for the future — not just its own, but that of the 8 million kids watching them, those 8 million kids dreaming and believing that they, too, could one day play in a World Cup for the U.S.

They just have to figure out how to get there.

Andrew Lewellen (@AndrewHLewellen), a former college soccer player and youth coach, has written about the sport for ESPN The Magazine, ESPN.com, The New York Times, and other publications.