Final answer:
A byproduct of war propaganda in the U.S. during WWI was increased distrust of German immigrants, as propaganda aimed to promote national unity and loyalty which inadvertently led to suspicion towards those of German descent.
Step-by-step explanation:
A byproduct of war propaganda posters in the U.S. during World War I was an increased distrust of German immigrants. Propaganda was a tool used by the U.S. government to gain support for the war effort, emphasizing patriotism and loyalty to America. At a time when many immigrants had ties to their countries of origin, including Germany, these posters often fostered suspicion and hostility towards those of German descent by promoting a message of unity under American identity, disregarding their ethnic backgrounds.
This was further exacerbated by anti-German sentiment following events like the sinking of the RMS Lusitania and the Zimmerman Telegram. The distrust went to the extent that even speaking German or owning German books could become grounds for suspicion and accusation.