Final answer:
The sinking of the Lusitania influenced American sentiment but did not immediately cause the U.S. entry into World War I. It was a factor among several that led to increased tensions with Germany, contributing to the context in which the U.S. eventually declared war in 1917. Therefore, the correct option is A.
Step-by-step explanation:
According to Walter Lippmann, the sinking of the Lusitania led to a shift in American sentiment regarding World War I, but it was not the immediate cause of the U.S. entry into the conflict. The Lusitania was sunk by a German U-boat on May 7, 1915, and resulted in the loss of 1,200 lives, including 128 Americans. The ship was carrying a significant amount of war materials, which was cited by Germany as justification for the attack, claiming it as an act of self-defense. Despite Germany's warnings about the risks of traveling on British vessels, the attack on the Lusitania was largely viewed by the American public as an unprovoked aggression. This caused outrage and contributed to a negative view of Germany, leading to increased tensions.
However, the Lusitania's sinking did not immediately bring the U.S. into the war. President Woodrow Wilson maintained a stance of neutrality for a time, even after the incident. It wasn't until 1917, after the resumption of unrestricted submarine warfare by Germany, which included the sinking of American ships and the discovery of the Zimmermann Telegram, that the U.S. declared war on Germany. The sinking of the Lusitania thus influenced the context in which the U.S. eventually entered WWI, but was one among several factors.