On the morning of April 10, 2018, a group of nearly 150 people filed into an ornate, wood-paneled courtroom at the Prettyman Federal Courthouse in Washington, D.C. There they waited—a little longer, yet—to become naturalized American citizens.

Among this group was David Storey, a television news producer. Originally from Scotland, Storey moved to the United States as a 16-year-old, landing in New York as a high school exchange student. That was 24 years ago. Storey has not been back to Scotland since, at least not to live.

That morning, he was dressed smartly in a well-tailored blue suit, a crisp white button-down shirt and a striped tie. His seat was assigned in the front row, directly across from the dais where two judges would preside over a ceremony that promised to transform ...