Who was the leader of the American Expeditionary Force?

General John Pershing. President Wilson's possible first choice, Fredrick Funston died of a heart attack.

Interestingly did not end segregation even though he was a supporter of black soldiers in the Army, having spent much time with the 10th calvary. He had been called "Black Jack" and worse because of this association and other reasons.https://en.wikipedia.org/wiki/John_J._Pershing