These words are used interchangeably, but careful writers distinguish between them. A nation is primarily a body of people who are associated with a particular territory. A country is a tract of land, a territory, that incidentally is the home of certain people. Emphasis upon either people or area is suggested in these sentences: "The United States is a nation of diverse peoples." "The United States is a country of vast dimensions."
Dictionary of problem words and expressions. Harry Shaw. 1975.