The saying “one nation under God” is a part of the Pledge of Allegiance of the United States of America. An early version of the pledge was composed in 1885 by Captain George Thatcher Balch. Balch was an officer in the Union Army during the Civil War who wanted to find ways to teach patriotism to young children in the public schools. A few years later, in 1892, Francis Bellamy, a Baptist pastor from New York, significantly revised and expanded Balch’s original pledge in an effort to promote the 1893 World Fair. This version of the pledge went largely unaltered for decades when Congress officially adopted it in 1942 at the start of World War II.
However, the saying “one nation under God” was not a part of Bellamy’s pledge (the original draft simply stated, “One nation, indivisible”). In fact, Bellamy staunchly believed in the separation of Church and State and intentionally did not include any references to God in the pledge. It wasn’t until 1954 under the direction of President Eisenhower that the words “under God” were added to the pledge. This was mostly due to the growing fear of communism throughout the United States during the Cold War.
The inclusion of the phrase under God was meant to reaffirm America’s heritage as a predominately Judeo-Christian nation in the face of looming global threats (especially ones that were derived from atheistic, materialist worldviews such as communism). Having just come out of World War II, and with the Cold War in full swing, President Eisenhower sought to unify the nation and proclaim trust in God against destructive, godless forces.
In short, the saying “one nation under God” is simply the call of a citizenry to be a unified nation that trusts God to protect them from harmful and evil forces.
Is it wrong to pledge your allegiance to the country in which you are a citizen? No, the Bible does not forbid such an action. In fact, unity among the citizenry of a nation is a good and virtuous thing to pursue, so long as that nation is not directly contradicting the Word of God in its governance.
Ultimately, as Christians, our allegiance is to God alone. His Word is to be the ultimate authority in our lives (Joshua 1:8; 2 Timothy 3:16–17) as we seek to be good citizens of our nations (Matthew 22:21; Romans 13:1–3; Titus 3:1). In fact, the Bible puts a strong emphasis on being unified as God’s people as we live and interact with one another in our daily lives (John 17:11; Romans 15:5–6; Ephesians 4:3). So, in a nation like the United States where the majority of people identify as Christian, being “one nation under God” would be a natural outflow of living according to the biblical commands for unity.