This US-made postcard is captioned "Constitutionalist Soldiers, Mexico"; in the lower left corner is "Max Stein, Chi." [probably Chihuahua, a Mexican state, where he was based.]
These are typical images which would appear in newspapers of the time and postcards would be another way to get the image out and make some money besides.
To my eye, the machine gun placement is less than ideal in the upper image; wouldn't you have to remove the men with rifles at the front in order to shoot the machine gun?