Final answer:
The United States responded to Japan's expansion into China in French Indochina by remaining neutral and imposing economic sanctions.
Step-by-step explanation:
The United States responded to Japan's expansion into China in French Indochina in late 1930 by d) Remaining neutral.
Despite the shock and dismay at the brutality of the war in Asia, the US government did little to intervene. Even after a film of the sinking of the USS Panay showed Japanese fighter planes gunning down survivors, the majority of Americans believed that recent events demanded withdrawal from the region rather than sending more military forces. Instead, the US imposed economic sanctions by banning the sale of war materials to Japan.
These actions ultimately led Japan to plan a surprise assault on Pearl Harbor and the United States entered World War II.