Final answer:
The U.S. protested against Japan's aggressive actions towards China, including severe human rights abuses and territorial expansion. Economic sanctions and embargoes by the U.S. failed to stop Japanese aggression, culminating in the attack on Pearl Harbor and the U.S.'s entry into World War II.
Step-by-step explanation:
The United States protested against Japan for what they were doing to China. Despite not being at war at the time, the U.S. took issue with Japan's actions, such as the creation of a puppet state called Manchukuo from Chinese territory and the horrific events that took place during the invasion of China, including the atrocities committed by Japanese soldiers in Nanjing (Nanking). The U.S. response included economic sanctions, such as an embargo on oil and gas sales to Japan, which ultimately led to further Japanese expansionism in Southeast Asia and the surprise attack on Pearl Harbor by Japan.
The U.S. aimed to pressure Japan into ceasing its aggressive expansion and brutal attacks throughout Asia, particularly in China, but diplomatic efforts ultimately failed, leading to a significant shift in U.S. foreign policy from isolationism to engagement in World War II after the attack on Pearl Harbor.