Which factor most contributed to the united states' decision to enter world war 1

Germany attacked merchant ships that carried American citizens (APEX)

When war began in 1914, the U.S. decided to remain neutral. However they entered the war in 1917 mainly because the German ambassador announced the continuation of submarine warfare, and ended diplomatic relations with the U.S. And also because a foreign minister, in an attempt to eliminate the threat of American involvement in Europe, tried to provoke Mexico and Japan into attacking the U.S., a message containing the minister's intent was decoded by the British and sent to the U.S. Because of these two reasons President Wilson asked Congress for permission to go to war.

Yes it is appropriate I first saw it when i was 13 (i’m 16 now) and it wasn’t inappropriate but it did include a lot of violence. If you don’t want him to see violence I don’t recommend. Otherwise, it’s a lovely movie!