The song is from Mr. President, which was the last musical that Irving Berlin wrote. It starred film actor Robert Ryan, Nanette Fabray, and featured a young Anita Gillette who most recently played Tina Fey's mother several times in 30 Rock.
The musical basically centers on the personal life of the president and his family, with a smattering of politics thrown in. The book is by Howard Lindsay and Russel Crouse, who among many other shows, from the book for
The Sound of Music. So the pedigree was certainly strong.
The show opened in 1962, but got only mediocre reviews. It didn't have a great run, but was semi-respectable with 265 performances. The book was considered a bit old-fashioned, as was the score which isn't particularly distinguished, though does have a handful of wonderful numbers, most notably "They Love Me" sung by Nanette Fabray as the First Lady, and "The Secret Service" (Makes Me Nervous) sung by Ms. Gilette as their daughter. And this song below, that Ryan sings at the end of the show.
The song is the last song in the show. And this is the last show that Irving Berlin wrote. And the last words are about as quintessential Irving Berlin as perhaps any words could be. I don't know if this is the last song he wrote for the show -- I doubt it. But it's the last original Irving Berlin song ever performed on Broadway. And that's what I love so much about it: if you had to pick the last words of the last song of the last show that Irving Berlin wrote -- the man who wrote such grandly, heart-on-your-sleeve patriotic songs as "God Bless America" and "Give Me Your Tired, Your Poor" and "This is the Army, Mr. Jones" (not to mention "I Like Ike" and "Miss Liberty" and more) -- this is how you'd want to go out.
This song is "This is a Great Country." And the last words are...oh, you'll hear them. Hey, it's the Fourth of July. You deserve the fireworks.
This, folks, is how you make an exit.