Interesting to see the variations - aside from the US Marine turned to British soldier, I note this version tones down the hyper-"patriotic" stuff -

"I put on his T-shirt of gray and of black
With an eagle and an Army patch embroidered on the back.

And although it barely fit me, I began to swell with pride
And for a shining moment I was United States Army deep inside..."

The folk process in an Internet age. And, as so often, the folk process knows which bits to leave out.