Final answer:
The patriotic song written by Katharine Lee Bates that is often seen as an unofficial anthem of the United States is 'America the Beautiful'.
Step-by-step explanation:
The patriotic song written by Katharine Lee Bates that is considered an unofficial anthem of the United States is America the Beautiful. It praises the beauty and ideals of America and, unlike The Star-Spangled Banner, which was inspired by the British bombardment of Baltimore and became the official national anthem, America the Beautiful serves more as an expression of national pride and affection for the country's landscape and values. My Country 'Tis of Thee and Battle Hymn of the Republic are also well-known patriotic songs, but are not penned by Bates.