Triple Alliance frustration with France regarding their Colonies in Africa
France Alliance with Russia and the British , known as the Triple Entente
The annexation of Serbia by the Austria - Hungarian Empire after the Assassination of the Archduke of Ferdinand
There was a secret alliance between Germany, Austria Hungary and Italy and they were growing tired of France and Britain conquests in Northern Africa.
The British Loans with JP Morgan Bank
There was a secret alliance between France, Britain and Russia
Sinking of the RMS Lisutania
The assassination of the Archduke Ferdinand of the Austria - Hungarian Empire was blamed on the Serbs. Serbia had an alliance with Russia, so when the Austrian Hungarian Empire made offensive advancements into Serbia, Russia had to intervene. And so this caused a chain reaction, leading to the war between both alliances against each other.
US Declaration of War
JP Morgan Bank loaned great amounts of money to the British as the British bought their war supplies from the US. By 1917, the British had used up all of their collateral and the US was under risk of losing all of the loans that the British took from the US. So, it can be inferred that one of the incentives for the US to involve themselves in WWI was to recover their loans for a profit.
The sinking of the US ship RMS Lisutania by the Germans led to a lot of public anger as it was unprovoked.
The US declared war on Germany on April 2, 1917 under the presidency of Woodrow Wilson. The US stated the reasons behind the involvement as Germany was the 'Enemy of Liberty' and so the US involvement would attempt to restate liberty of the people affected by the Germans.