Armstrong was born and raised in Washington, D.C. When he was 11, a local youth soccer coach spotted Armstrong playing soccer and recruited him into the coach's youth team. From that point on Armstrong moved into high school, college, and national team soccer. He attended Howard High School in Ellicott City, Maryland. Armstrong's college career was spent at the University of Maryland, where he was first team All ACC in 1984 and 1985 and second team All ACC in 1983. He played in a total of 78 games for the university, tallying 24 goals and 18 assists. In 1986, he was part of the Fairfax Spartans club which won the National Amateur Cup, defeating St. Louis Busch 3-0. The Spartans featured other national team players John Kerr, Bruce Murray and John Stollmeyer in addition to Armstrong.
Professional
Armstrong played two seasons for the Cleveland Force of the Major Indoor Soccer League from 1986 to 1988. At the end of the 1987-1988 season, he transferred to the Baltimore Blast. However, on January 14, 1989, he broke his leg midway through the season. In February 1991, he signed with Santos of the Brazilian First Division making Armstrong the first American player ever to sign a professional contract in Brazil. Upon completing the season Armstrong returned to the U.S. with the Maryland Bays, in the American Professional Soccer League. That year, the Bays made it to the league semifinals before falling to the Albany Capitals. In 1995, he moved to the Washington Warthogs of the Continental Indoor Soccer Leagueon loan from Major League Soccer as he was the fifth player signed to the new league. Armstrong decided to compete with the Charlotte Eagles of the United Soccer Leagues/ USISL for the 1996 season opting out of his contract with Major League Soccer and later retiring from the game at the age of 31. That year he was selected to the USISL All Pro League Team.
National team
His first appearance for the United States national team came in 1987 in a match against Egypt. He was also a member of the Olympic team in the 1988 Summer Olympics in Seoul, South Korea. His performance with the Olympic team made him a mainstay on the national team through the early 1990s, playing in all three of USA's games of the 1990 FIFA World Cup. He made a total of 81 appearances for the national team, though he never scored a goal at this level.
Coach
Since his retirement from international soccer, he has remained active in coaching and community initiatives. He has spent time organizing for inner-city Christian Ministries programs such as Soccer Beats. In the mid-1990s he coached the USA Hurricanes club level soccer team in Charlotte, NC. In 1999, he became the head coach of the Montreat College Cavaliers in Montreat, North Carolina which play in the NAIA. He remained in this position until his retirement in 2006. Armstrong also coached the youth team '85 HFC Vipers of Asheville, North Carolina from 2000-2004. After leaving Montreat, Armstrong joined the youth club, Bethesda Roadrunners, as its head coach. He also created another section of Heroes FA, in Maryland and is currently their head coach and technical director. He is also the Director of Recruiting in Ohio for Brad Friedel's Premier Soccer Academies. He was named technical director of Rocket City United on December 11, 2009.
