請問美國係第一次世界大戰點解要向德國宣戰?(英文)(10分)

Since the Germany adopted the policy of " Restricted Submarine Warfare " , the Germans wanted to bombed the ships of Britain but she also bombed the merchant ships of USA , so this led to a lot of deaths in USA and thus the USA declared war to Germany .

Besides the unrestricted submarine warfare, Germany proposed forming an alliance with Mexico against the U.S. This further angered the us, so the us declared war on Germany.