Christmas celebrated around the United States in 1930s

The transcript describes the powerful and unified call of bells from the steeples of Christendom, which resonates as a single voice across cities and snowy country miles. This collective sound invites a global response, urging the world to listen and react to the harmonious call.

In what way does the text suggest a collective response from the world?

What is the significance of the phrase 'a single song' in the text?