In 2024, he was named Southeastern Conference (SEC) Coach of the Year at Mississippi State.
Raised in the small English village of Embsay, Armstrong grew up in a soccer family supporting Manchester United.
After college, he began working for the United States Soccer Federation as the equipment manager for the national women's under-19 team.
He later spent a decade working for Lonestar SC, a youth club based in Austin, Texas.
[3] In his final season in Starkville, he led Mississippi State to go 10–0 in conference play to claim the first Southeastern Conference (SEC) regular-season title in program history, which led him to be named SEC Coach of the Year.