Question: What is shared by the official U.S. state song "The Song of Iowa" and the German Christmas song "O Tannenbaum"?

Context articles: The Song of Iowa
List of U.S. state songs
Hail, Vermont!
Sweet Virginia Breeze
The Old North State (song)
Así Es Nuevo Méjico
Old New Hampshire
Illinois (state song)
Maryland, My Maryland
O Tannenbaum

"The Song of Iowa" is the official state song of the U.S. state of Iowa, written by S. H. M. Byers in 1897 and adopted by Iowa State Legislature in 1911.
 The song is set to the tune O Tannenbaum and Byres' lyrics' theme is centered on his love and praise for Iowa.
Forty-nine of the fifty U.S. states that make up the United States of America have one or more state songs, which are selected by each state legislature, and/or state governor, as a symbol (or emblem) of that particular U.S. state.
 New Jersey does not have an official state song, while Virginia's previous state song, "Carry Me Back to Old Virginny", adopted in 1940, was rescinded due to its racist language by the Virginia General Assembly.
 In 2015, "Our Great Virginia" was made the new state song of Virginia.
"Hail, Vermont!"
 was the former state song of the U.S. state of Vermont.
 The song was written by Josephine Hovey Perry of Barre, Vermont, and was officially made the state song in 1938.
 The song was significant at its time of publication for mentioning Vermont's daughters as well as her sons.
 From the 1950s through the 1960s the song was given to Vermont school children in a soft-bound booklet titled "Vermont Sings."
 On May 22, 2000, the song was replaced by "'These Green Mountains."'
"Sweet Virginia Breeze" is the official Popular State Song of Virginia.
 While collaborating in 1978, Richmond artists Steve Bassett and Robbin Thompson wrote "Sweet Virginia Breeze" during a rehearsal for their concert at Virginia Commonwealth University.
 The first studio recording of the song was on their album "Together" in 1978.
 Other versions of the song have been released by both Bassett and Thompson on some of their solo albums throughout their careers such as Thompson's 1980 album "Two B's Please" and Bassett's 2006 album "Blowin Dust Off".
 In 2015, by a vote of 39-0, "Sweet Virginia Breeze" was designated the official popular state song of Virginia along with "Our Great Virginia" as the official traditional state song.
"The Old North State" is the official state song of the U.S. state of North Carolina.
 Written by William Gaston in 1835 and set to an arrangement composed by Mrs. E.E. Randolph in 1926, it was adopted as the state song by the North Carolina General Assembly in 1927.
Así Es Nuevo Méjico (English: "Such Is New Mexico") is the official Spanish language State Song of the U.S. State of New Mexico.
 The words and music were created by contemporary composer Amadeo Lucero.
 It was performed with guitar accompaniment to the assembled members of the Legislature by Lieutenant Governor Roberto Mondragón at the opening session in 1971.
 It was enthusiastically received and promptly adopted as the Spanish-language version of the State Song.
"Old New Hampshire" is the original and official state song of the U.S. state of New Hampshire.
 The words were written by Dr. John F. Holmes and music composed by Maurice Hoffmann in 1926.
 In "Old New Hampshire" was chosen to be the "official" state song first in 1949, then again in November 1977, by the State Song Selection Board.
 New Hampshire has eight "honorary" state songs, and no other official songs.
"Illinois" is the official state song of the U.S. state of Illinois.
 Written by Charles H. Chamberlain (1841–1894, also spelled Chamberlin) and composed by Archibald Johnston (died 1887), "Illinois" became the state song by an act of the 54th Illinois General Assembly (1925).
"Maryland, My Maryland" is the official state song of the U.S. state of Maryland.
 The song is set to the melody of "Lauriger Horatius" — the same tune "O Tannenbaum" was taken from.
 The lyrics are from a nine-stanza poem written by James Ryder Randall (1839–1908) in 1861.
 The state's general assembly adopted "Maryland, My Maryland" as the state song on April 29, 1939.
"O Tannenbaum " (] ; "O fir tree") is a German Christmas song.
 Based on a traditional folk song, it became associated with the traditional Christmas tree by the early 20th century and sung as a Christmas carol.