As a young woman, Moon fell for a Canadian man and moved to Toronto. The 59-year-old homemaker, who still visits the U.S. to see relatives, said she feels American in her bones, even after three decades abroad. Yet despite her deep roots, Moon walked into a U.S. consulate two years ago, raised her right hand and recited an oath renouncing her U.S. citizenship. Afterward, she said, "I bawled my eyes out."

 Moon is among record numbers of Americans cutting ties. U.S. offices abroad reported that 1,001 U.S. citizens and green-card holders had renounced their allegiance in the first three months of the year, according to Andrew Mitchel, a lawyer in Centerbrook, Conn., who analyzes Treasury Department data. That figure puts 2014 on track to top last year's total of 2,999 renunciations, he said, which was the most since the government began disclosing the data.