LIKE MANY TRULY GREAT athletes, United States women's national team defender Meghan Klingenberg found her greatest motivation in a moment of pain. An alternate on the U.S.'s 2012 Olympic squad, Klingenberg was with the team in London, but forced to watch her friends and colleagues win gold from the sidelines.

For the 26-year-old Pennsylvania native, that bittersweet moment was a turning point. Speaking with American Soccer Now, Klingenberg said, "It was such a happy moment, but excruciating at the same time."

"For [the alternates], it was great to see our teammates win gold because we felt like we helped them get there, but it was such a bummer not being able to be a part of it. It was a really big turning point in my career. I felt like 'I can't do this again. I don't want to do this again. I want to be on the team.' That's when I made the decision to go abroad and invest in the game."

Following the Olympics, Klingenberg signed with Swedish club Tyreso and eventually went on to play in a Champions League final. That success would lead to more opportunities with the national team and, this week, after two years of pain and sacrifice, Klingenberg's hard work paid off when she was named to the U.S.'s 20-player roster for the upcoming CONCACAF World Cup qualifying tournament.

The dream of representing the U.S. in a major tournament on the international level has motivated Klingenberg since she was a kid, sparked when she first watched a collegiate soccer game with her mother.

"[Representing the U.S.] is something I've wanted to do since I was little. When I was nine, I watched [a college soccer match] with my mom," Klingenberg said. "I asked, 'What's past college?' and she showed me the U.S. women's national team. It's always been something I've wanted to pursue."

But making the roster for the World Cup qualifiers isn't enough. The University of North Carolina alum realizes that there is still work to be done.

"This is a step toward my goal of making a World Cup squad," she said. "I've been on the team for a couple years now and I've only ever been an alternate at the Olympics—which was a really cool experience. I got to learn a lot of things and be at a big tournament and understand the environment. But I've never actually been a part of a [major tournament] roster."

Since 2012, the U.S. squad has been one in transition. Former coach Pia Sundhage left to coach her native Sweden and the U.S. has since hired and fired another coach, Tom Sermanni, before bringing in Jill Ellis to guide the team to the 2015 World Cup in Canada. The roster has also been in flux, especially in the back.

After the London Olympics, Heather Mitts retired. Amy LePeilbet also dropped off the national team's radar following knee surgery. But two other defensive veterans, Stephanie Cox, who represented the U.S. at the 2011 World Cup, and Rachel Van Hollebeke, who was a regular starter at both the 2011 World Cup and 2012 Olympics, were both still in the running for spots on the World Cup qualifying roster heading into last month's games against Mexico.

In those games, Klingenberg took her chance. Being one of the standouts for the U.S. against Mexico helped her parlay those strong performances into a spot on the roster for World Cup qualifying—even beating out well-known veterans like Cox and Van Hollebeke.

Klingenberg was quick to recognize how tough the competition is for spots on the U.S. squad.

"There were some really great players who did not make the squad," she said. "I've learned so much from playing with them. They've been such a big part of the U.S. women's national team and I've loved playing with them."

In this month's CONCACAF qualifying tournament, the U.S. will be playing for one of three slots in next summer's World Cup—a seemingly easy task. Canada, the U.S.'s main rival in the region, doesn't have to qualify because it's hosting the tournament. And Mexico, the only other team with a realistic shot at beating the U.S., lost its last two games to the Americans by a combined score of 12-0.

But Klingenberg isn't taking anything for granted and insists there's still plenty of work to be done.

"There's always challenges. We've done well in CONCACAF and hopefully we'll continue to do well, but there's always personal challenges, team challenges," Klingenberg said. "We're absolutely taking this as seriously as possible. We're going to challenge ourselves every single game. You can't take anyone for granted."

Klingenberg also sees the value in every training camp with the U.S. because of the team's outstanding depth. Just getting through a training session can be a considerable challenge.

"On crosses, Abby [Wambach] is one of the hardest people to defend in the world. If you're talking about 1 v. 1, take your pick. Amy Rodriguez is great, Sydney Leroux is fast, Alex can get in behind you," Klingenberg said. "Everyone challenges you in a different way."

Klingenberg's journey to Europe ended this spring when she came back to NWSL and the Houston Dash, but her experiences overseas have continued to pay dividends on the national team. Two of her teammates at Tyreso, Christen Press and Whitney Engen, also happen to be her teammates on the U.S. national team.

"When you play with someone that long, you learn their tendencies, what they look for, how they like to play," Klingenberg said. "I understand Christen's movement off the ball really well. When she's in the box and I'm crossing, I know every single time where she's going to go. The same with Whitney. I know if I'm stepping, she's going to step in behind. It's just a comfort factor."

But as good as Klingenberg's journey to Europe was for her international prospects, it wasn't without pain. Last spring, Tyreso advanced to the Champions League final to face defending champions Wolfsburg. Tyreso took the lead twice in the match, but eventually lost 4-3. The pain of coming so close to a European championship lingers.

"They're starting tomorrow with the first round of the [2014-15] Champions League. [Whitney, Christen, and I] were just discussing today how much it hurts because we don't know if we'll ever be back there again. We came so close and weren't able to pull it off."

For the time being, however, her focus will remain squarely on the U.S. and making the 2015 World Cup squad.

Playing in the World Cup "is my ultimate goal in soccer," she said. "That's what I work for. I love the game. I love my sport. I love the lifestyle and my teammates, but that's my ultimate goal.

"It would be such a fulfilling experience."

John D. Halloran is an American Soccer Now columnist. Follow him on Twitter.