What were the official reasons the united states became involved in european conflict

Zimmerman Telegraph - In 1917, German Foreign Minister Arthur Zimmermann sent a telegram to Mexico suggesting that if the US should declare war on Germany, Mexico should declare war on the US. In return, Mexico would get back the territory lost in the Mexican-American War (Texas, New Mexico, and Arizona).

The Sinking of the Lusitania - In May 1915, a German U-boat sunk the British passenger ship Lusitania off the coast of Ireland. Over 1,000 passengers were killed, including 128 Americans.