Final answer:
In 1914, the United States chose neutrality following the outbreak of World War I after the assassination of Franz Ferdinand. It was only in 1917 that the U.S. joined the Allies, influenced by events such as the sinking of the Lusitania and the Zimmerman Telegram.
Step-by-step explanation:
When fighting broke out after the death of Franz Ferdinand in 1914, the stance of the United States was initially to remain neutral. President Woodrow Wilson and the American public largely favored isolationism, preferring not to become entangled in the European conflict. Despite being an ally of Britain and providing supplies and low-interest loans, the U.S. did not formally join the war until 1917, following provocations such as the Lusitania sinking and the Zimmerman Telegram, which shifted American public opinion and led to intervention on the side of the Allied powers.