How about Glen Campbell's Galveston? Though not specifically mentioning the civil war or the confederacy, the fact that the singer is from Galveston Texas, and is watching "the cannons flashing" heavily implies both.

Galveston, oh Galveston, I still hear your sea winds blowin'
I still see her dark eyes glowin'
She was 21 when I left Galveston

Galveston, oh Galveston, I still hear your sea waves crashing
While I watch the cannons flashing
I clean my gun and dream of Galveston

I still see her standing by the water
Standing there lookin' out to sea
And is she waiting there for me?
On the beach where we used to run

Galveston, oh Galveston, I am so afraid of dying
Before I dry the tears she's crying
Before I watch your sea birds flying in the sun
At Galveston, at Galveston