Star Spangled Banner full version.

I have pledged allegiance to the USA many years ago. And since I was naturalized as a citizen of the USA, I have not really learned the national anthem. It was not required for citizenship to begin with. But recently, I wanted to learn how to sing it. So I goggled the lyrics and boy was I surprise to learn that it is 4x longer that what I have heard it sang before. Obviously, during events when people sing the Star Spangled Banner, people only sing the first stanza. Now I wonder how many Americans can really sing all the 4 stanzas of the poem. In fact I wonder how many Americans can sing the first stanza. Here is the lyrics of all 4 stanzas.