The sinking of the Lusitania shows that America was hesitant to enter World War I. The Lusitania was a British ship that had American soldiers on it. This ship was traveling to Ireland but was shot down by the German military. This use of unrestricted submarine warfare resulted in the deaths of thousands of individuals, including over 100 American citizens.
This event, that took place in May of 1915. Even though this causes outrage among citizens, the US does not formally declare war against Germany until they find out about the Zimmerman Telegram (in 1917). This shows that America tried to avoid entering World War I at all costs.
