Which event most clearly influenced the U. S. decision to enter World War I on the Allied side?

Germany sunk the Lusitania causing 128 American deaths

Explanation:

On May 7, 1915 a German U-boat torpedoed the British-owned luxury steamship Lusitania, which killed 1,195 people. Which is including 128 Americans which is according to the Library of Congress.

I hope this helped. I am sorry if you get this wrong.

Germany sunk the Lusitania, causing 128 American deaths.

Explanation:

However, if you look into the history of the events leading to the US joining the war, you will see that the United States told Germany to "back off" meaning that the US gave a fair warning to Germany telling them to stop (sinking ships and blocking supply lines). And if they did not stop, the US would join the war on the Allied side.

You can also you this Quizlet that I found to answer any of your other questions.

https://quizlet.com/271293829/211-us-history-flash-cards/#:~:text=Which%20event%20most%20clearly%20influenced,Lusitania%2C%20causing%20128%20American%20deaths.&text=What%20was%20the%20impact%20of,bolstered%20the%20French%20and%20British.