United States vs United States of America

United States

name
  • Includes the land area, internal waters, territorial sea, and airspace of the United States. 

  • Federal nation consisting of several states, actual, historical or hypothetical. 

  • The collection of individual states of the United States of America. 

United States of America

name
  • A country in North America, stretching from the Atlantic to the Pacific Ocean, and including Alaska, Hawaii, and several territories. 

How often have the words United States and United States of America occurred in a corpus of books? (source: Google Ngram Viewer )