Lee Greenwood’s “God Bless the U.S.A.” has become former President Donald J. Trump’s unofficial theme music on the campaign trail. Here at the Republican National Convention in Milwaukee, the song was performed live by none other than Mr. Greenwood himself, as Mr. Trump walked into the arena on Monday. The anthem, released in 1984, is essentially a song about togetherness and the diversity of the United States. And it’s now become tied to a candidate who has often represented division and chaos. As Mr. Trump is set to deliver the culminating address at the convention today with a newfound message of unity, we explore that message — through the song that has become his soundtrack. We talk to Republicans, including Mr. Greenwood, about what defines American values and whether those values are reflected in the candidacy of Mr. Trump. On today’s episode: Lee Greenwood, country music star