Us entrance into world war 1 in 1914, us president wilson declared a proclamation of neutrality. On april 2, 1917 wilson declared war on germany because: unrestricted submarine warfare. the sinking of the lusitania killed many americans which brought a severe warning from wilson to germany in 1915. The zimmerman note (1917) was a message sent by the german foreign. Minister (zimmerman) to mexico pledging germany"s support in the form of weapons and even men if they declare war on the u. s. It was intercepted and printed in papers around the world. Many u. s. citizens supported the allies rather than the central powers. We feared that we would become germany"s next victim. Significance of us entrance in ww1: the war turned in favor of the allies, broke the us policy of isolation (foreign policy in which the nation stays out of other nation"s affairs. , us emerged as a world power.