What event finally caused the United States to enter World War 1

America originally desired to remain neutral in WWI. However through submarine warfare, the Germans sunk the British Lusitania cruise, which contained American passengers. The US President Woodrow Wilson still remained neutral however, the US intercepted a telegraph from Germany to Mexico that implored Mexico to attack the US. The Germans were fearful of US entry and tried to distract the US, and this telegraph became known as the Zimmerman Telegraph. Afterwards, the US finally entered war on the Allied side.

Serbian-nationalist terrorist group called the Black Hand sent groups to assassinate the Archduke ... (alliances, imperialism, militarism, nationalism) was the assassination