In 1915, he took a position as research associate in primitive philology at the Carnegie Institution in Washington, D.C.[1] While working for the Committee on Public Information during World War I, he suffered a skull fracture inflicted by an enemy spy.

After an extended stay in Samoa where he studied the local language, he visited Australia, New Zealand, and Fiji, where he managed a business.

He returned to the United States in 1898 and resumed working in journalism, becoming the literary editor at the Sun newspaper in New York.

Churchill was a prolific writer whose work included scientific articles, magazine pieces, reviews, and books on the life and customs of the indigenous peoples of the South Pacific Islands.

He was a member of several scientific organizations, including the Royal Anthropological Institute of Great Britain and Ireland and the American Association for the Advancement of Science.