Answer:
The United States president during the first World War was Woodrow Wilson
Step-by-step explanation:
In January 1917, Germany starts a policy that implies unrestricted submarine war against the ships close to some islands that belongs to United Kingdom. After an attack to some American ships the president Wilson discuss the idea to enter in the war with his cabinet. all the members agreed and in march 20th of 1917 US enter to the war.