How did many celebrities, such as Charlie Chaplin, contribute to the American war effort
during World War I?

They helped promote bonds that helped America fund the war, known as Liberty Bonds

Many European celebrities were secretly pacing information to American intelligence services

They appeared in propaganda spots where they mocked the German Kaiser, thus making him
less threatening and raising American morale

They significantly helped Woodrow Wilson in reelection campaign which he ran on the premise
that he would intervene in what was then called The Great War