The earliest version of the full "hymn" that I've discovered, nearly five years before the U.S. entered World War I:

From the "San Francisco Sunday Call" (Nov. 17, 1912), p. [16]: "If you know the marines so well that they don't fear you'll think they are boasting, they will sing you their hymn:

From the halls of Montezuma
    To the shores of Tripoli
We fight our country's battles
    On the land and on the sea;
Admiration of the nation,
      We're the finest ever seen,
And we glory in the title
      Of United States marine.

From the hell hole at Cavite
      To the ditch of Panama
You will find them very needy
      Of marines – that's what we are;
We're the watch dogs of a pile of coal,
      Or we dig a magazine.
Though our joblots they be manifold,
    Who would not be a marine?

Our flag's unfurled to every breeze
      From dawn to setting sun;
We have fought in every clime and place
      Where we could take a gun.
In the snows of far-off northern lands
       And in sunny tropic scenes,
You will find us always on the job,
      The United States marines."

Here's health to you and to our corps,
      Which we are proud to serve,
In many a strife we have fought for life
       And never lost our nerve.
If the army and the navy
Ever look on heaven's scenes,
They will find the streets are guarded by
The United States marines.

You don't need to be a professional publicist to see why stanza 2 got the deep-six.