Final answer:
America's most popular Christmas song is often cited as "White Christmas," written by Irving Berlin and sung by Bing Crosby, capturing a traditional and nostalgic essence of the holiday.
Step-by-step explanation:
The Christmas song often considered as America's most popular is "White Christmas", written by Irving Berlin and famously sung by Bing Crosby. This song has a nostalgic quality that captures the essence of the Christmas spirit for many. It speaks to a traditional, ideal holiday season with its imagery of snow and peacefulness. The relevance of I Hear America Singing in this context is as an expression of the varied and collective spirit of celebration that can be found in America's diverse traditions, including those of Christmas carols and songs.