Bernays admits in Propaganda, the atrocities the U.S. fought against in WWI were "alleged." I got the impression that meant made up. For a new perspective on why the U.S. got into WWI, watch Robert Newman's "History of Oil" Try Googling it because I don't think it was ever released in the U.S.
You also get the impression a lot was made up in relation to WWI by Bernays's colleague Walter Lippmann. Propaganda is kind of like a Cliff Notes version of of Walter Lippmann's 1922 book Public Opinion
Also the introduction in this reprint of Propaganda by Mark Crispin Miller points you to Falsehood in Wartime: Propaganda Lies of the First World War, which was published in 1928 the same year Bernays published Propaganda.