OK, so Jurgen Klinsmann was right. The US couldn’t win the World Cup.

At least not yet. Tuesday’s 2-1 loss to Belgium in the Round of 16 drove that point home with every giveaway, every acrobatic save Tim Howard was forced to make.

So now the question is how does the US change that? How does it take the next step to reach a semifinal, or even win a World Cup?

It won’t be easy, or quick. Evolution is a slow, painful process. But it won’t be impossible, either. It’s not about playing better, but producing better players.

It’s in this team’s DNA to run fast, jump high and tackle hard. But to join the elite few capable of winning a World Cup, more is needed: ball control, first touch, possession. In essence, New York City FC sporting director Claudio Reyna told The Post, the team needs more skill, and an overhaul of the development system.

“Once the dust settles, the same questions will be asked about ability, skill level. We can compete, but we’re still not there yet,’’ Reyna said. “We still lack technical ability to create enough chances from combination plays. … Watching the Argentines and Colombians, their feet are like hands.

“The coaching throughout the country needs to be better. As youth technical director, I traveled around the country and the emphasis is still on the physical. For every team I saw trying to play the right way, we had 50 trying go the fast way for results. … It’s about running, tackling, athletes playing at a fast tempo, not about keeping the ball. That’s what we are, and our collective view needs to change.’’

As a former US World Cup captain, Reyna is qualified to know. But watching the struggles in possession contrast the Belgian’s comfort on the ball backed that up.

Blaming Klinsmann is as shortsighted as scapegoating predecessor Bob Bradley — his bigger job may not be coaching players but forcing change. After all, teaching first touch and ball control doesn’t happen at 30, but 13.

“We need to start developing technical players, able to possess the ball and attack better so that we’re the team creating 25 chances,’’ Landon Donovan told ESPN. “It takes time and we need young players like [Lionel] Messi, or [Romelu] Lukaku, players who make a big difference in the real games.’’

But those players don’t just go from the womb to the World Cup. They have to be identified, recruited and then developed, and the US pyramid — upside down from the rest of the world — has to do a better job of that.

“We’re focused more on Saturday and Sunday and less on Monday-through-Friday, the 365 days a year. Until we commit to make sure we truly develop players, we’re going to still be the team we are,’’ Reyna said.

“It’s a collective effort from MLS, US Soccer, youth clubs to take development seriously. … Spain, Germany, Holland, there’s no separation between club and country. We need to be working together. But it’s starting to happen.’’

The US Soccer Development Academy, instituted in 2007, identifies talent and eliminates pay-to-play, bringing lower-income players into the talent pool. But youth academies need to spend less time trying to win and more developing technical skills.

Given the title of technical director, Klinsmann has talked about making these changes. Germany made similar ones after a poor World Cup, and he coached the 2006 team to a third-place finish. Belgium reinvested the cash from hosting Euro 2000 into its development system, and the US saw the results firsthand Tuesday.

Young MLS fullback DeAndre Yedlin excelled at the World Cup, sending his agent’s phone ringing off the hook. But there are far more young US-eligible players coming through more advanced academies abroad — from Klinsmann’s point of view, the ones who haven’t picked the US yet are just ones he hasn’t successfully recruited yet.

“We’re looking for all Americans around the world,’’ Klinsmann said. “We have more coming through and that’s just part of globalization.’’

Bayern Munich’s 19-year-old Julian Green became the youngest player to score in a World Cup since Messi in 2006. But Klinsmann is also chasing 17-year-old Arsenal phenom Gedion Zelalem, several Mexican prospects and Augsburg striker Shawn Parker, who has scored in the Bundesliga and been capped at every level below the full German national team.

The U-17 won the Nike International Friendlies two of the last three years, routing Brazil 4-1 to do it; and this youth movement will be judged in the 2016 Brazil Olympics. With the Gold Cup, Copa America and World Cup qualifying, Klinsmann will have plenty of chances to show his wares as a coach. But his value may not be judged for years down the road.