Why did American ships become a target in 1917?

American ships became a target in 1917 primarily due to Germany's unrestricted submarine warfare policy, which aimed to cut off supplies to the Allies in World War I. As the U.S. increasingly supported the Allies through economic and military aid, German U-boats began attacking American merchant and passenger vessels. This aggressive strategy aimed to weaken the Allies by disrupting their supply lines and deter U.S. involvement in the war. The sinking of ships like the Lusitania further inflamed public sentiment in the U.S. against Germany, ultimately contributing to America's decision to enter the war.