Answer:
The sinking of American ships, the most popular one the Lusitania. The interception of the Zimmerman Telegram.
Step-by-step explanation:
After remaining neutral since the war's start, the United States entered World War I because Germany continued to wage unrestricted submarine warfare, which resulted in the sinking of American ships. The interception of the Zimmerman Telegram, in which Germany petitioned Mexico to join against the US, was another major factor. On April 6, 1917, Congress decided to declare war on Germany.