The United States did not get involved in World War I at its inception. It wasn't until March, 1915 that the first American was killed in circumstances linked to the war, the sinking of a British passenger ship. By February of 1916, president Wilson was promoting "Preparedness" in a cross-country speaking tour. The U.S. did not formally declare war on Germany until April 6, 1917. In 1915, when Battle Cry of the Mothers was published, WWI was still a European war.
Germany declared war on Russia, August 1, 1914. In December of 1914
the Germans completed the first air raid on Great Britain. February of
1915, Germany announces a "war zone" in British waters. By 1915, England,
France, Germany, Russia, Italy and others were embroiled in battle.
For more extensive information on World War I and its impact, see these sites: