I had thought it a reference to Sgt. Pepper.
But none of that matters.
“Sgt. Peppers?”
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Nope.
Think of the context of American Pie.
“The day the music died.”
All the other lyrics of the song refer to the “death” of rock and roll.
Sadler’s song, while admirably patriotic, was hardly “rock and roll”.
“The players tried to take the field
The marching band (military) refused to yield
Do you recall what was revealed
The day the music died”
Sgt Pepper’s was a good thing for rock and roll.
I wrote a high school English paper on American Pie. Got an A+.