This song is older than I thought. Lyrics below copied from FirstWorldWar.com. That page also has 2 audio files: one by Billy Murray from 1915, and one by Walter van Brunt from 1916.

The Lester S. Levy Collection of Sheet Music also has the sheet music.

The Record Lady's All-Time Country Favorites also has a recording of Gene Autry's WW2-era version, on Salute to Veterans Page 1. Autry doesn't sing the second verse.

DON'T BITE THE HAND THAT'S FEEDING YOU
(Words, Thomas Hoier. Music Jimmie Morgan. 1915)

Last night, as I lay a-sleeping,
A wonderful dream came to me.
I saw Uncle Sammy weeping
For his children from over the sea.
They had come to him, friendless and starving,
When from tyrant's oppression they fled,
But now they abuse and revile him,
Till at last in just anger he said:

CHORUS: "If you don't like your Uncle Sammy,
Then go back to your home o'er the sea,
To the land from where you came,
Whatever be its name,
But don't be ungrateful to me!
If you don't like the stars in Old Glory,
If you don't like the Red, White and Blue,
Then don't act like the cur in the story;
Don't bite the hand that's feeding you!"

"You recall the day you landed,
How I welcomed you to my shore?
When you came here empty handed,
And allegiance forever you swore?
I gathered you close to my bosom.
Of food and of clothes you got both.
So, when in trouble, I need you,
You will have to remember your oath." CHORUS