to reflect a hopeful, cohesive view of American society
To answer this question you need to picture America signing. He isn't talking about the physical space of America but rather the people that make up America. Picture everyone in America singing. They are together as a cohesive group singing one song. Also think about the purpose of singing. A majority of the time singing is used for positive reasons. It can lift the spirits. This also proves the hopeful part of the second option. The title tells us nothing about labor rights or success.
