Although Boxx was a member of the United States Under-21 national team pool, she did not receive her first senior cap until August 2003, when U.S. national team coach April Heinrichs named her to the team's 2003 FIFA Women's World Cup squad, making her the first uncapped player to be named to a U.S. Women's World Cup squad. Prior to the call-up, following the suspension of WUSA, Boxx had planned to take a coaching position at Cal State-Dominguez Hills and pursue a graduate degree at Pepperdine University.