The article notes that Congress added “under God” in 1954. That is correct but it’s not the whole story. It started with the pastor of the New York Avenue Presbyterian Church in Washington, DC, Dr. George Docherty, a native of Scotland.
Dr. Docherty thought this phrase needed to be added to the Pledge of Allegiance and in one of his sermons he said so, and among those in the congregation that day (not by accident) was President Dwight Eisenhower, a member of the Church. The President took the idea to key Congressmen and it was enacted into law.