What events led to the U. S. to join World War I?

I'm not sure but it has to be unrestricted submarine warfare

Unrestricted submarine warfare

Explanation:

Germany's resumption of submarine attacks on passenger and merchant ships in 1917 became the primary motivation behind Wilson's decision to lead the United States into World War I.

The Zimmerman Telegram was a secret diplomatic communication issued from the German Foreign Office in January 1917 that proposed a military alliance between Germany and Mexico if the United States entered World War I against Germany but was not the cause of the U.S. joining the war.

1. international: struggle for hegemony and empire outstrips the fiscal resources of the state

2. political conflict: conflict between the monarchy and the nobility over the “reform” of the tax system led to paralysis and bankruptcy.

3. the enlightenment: impulse for reform intensifies political conflicts; reinforces traditional aristocratic constitutionalism, one variant of which was laid out in montequieu’s spirit of the laws; introduces new notions of good government, the most radical being popular sovereignty, as in rousseau’s social contract [1762]; the attack on the regime and privileged class by the literary underground of “grub street; ” the broadening influence of public opinion.

4. social antagonisms between two rising groups: the aristocracy and the bourgeoisie

5. ineffective ruler: louis xvi

6. economic hardship, especially the agrarian crisis of 1788-89 generates popular discontent and disorders caused by food shortages.