U.S. American vs US-ian

U.S. American

noun

  • A person from the United States of America. 

adj

  • American 

US-ian

noun

  • An inhabitant or citizen of the United States of America. 

adj

  • Of or pertaining to the United States of America. 

How often have the words U.S. American and US-ian occurred in a corpus of books? (source: Google Ngram Viewer )