Trivia: America stayed neutral in World War I until Germany threatened what?
U.S. Navy ships
U.S. aircraft carriers
New York Harbor
Correct Answer: Commercial shipping
So why is this answer correct? : The U.S. declared neutrality in August 1914. In early 1915, Germany announced it would target all ships that entered the war zone. In March 1917, four U.S. commercial shipping boats were sunk by Germany, and America responded by declaring war in April 1917.