the reason america came into ww1 because Germany sunk a couple of ships that had america citizens on it one very famous the lusitania and cause the united states to enter the war this was one of the long term events. the other reason that started the war was the assassination of Austria Archduke Franz Ferdinand which caused the start of the war look at this web site and it will tell you every thing you need to know hope this helps
https://medium.com/@dhireshnathwani/what-was-the-most-significant-cause-of-world-war-one-ww1-74bb9e8...
