When in it's plural form, it refers to the continents of North and South America.
In it's singular form it is a colloquial term for the United States of America. However, people constantly scrutinize Americans for calling themselves American, since there are more "Americans." However, they fail to realize that:
1.) People are proud in their nationality. You will never hear a Mexican say "I'm an American. I live in D.F." Likewise you will never hear a German person say "I'm European."
2.) It is pretty stupid to say "Hi, I'm an United States of American."
America is one of the most hated countries in the world. Even though Americans are constantly helping other countries in national disasters and such; and a lot of deformed or seriously injured people travel to America from their countries to go to American hospitals. Yet, in return, Americans get their flags burned and verbally attacked. Also, most anti-Americans have never lived in the United States in their lives, so there is no base to their claims.
America is presided over by George W. Bush. Non-Americans assume that since he is our leader, Americans love and accept him. Because of that, Americans are subjected to more meanness. What they fail to realize is that the President has an approval rating of 27-34%; mostly in part because he is the one to blame for the poor state of the American economy, and the failed American education system. He also started two wars, which again, non-Americans assume Americans support, which again is false.
Contrary to popular belief, America is one of the mightiest nations in the world. It is NOT full of stupid people, and it is NOT full of fat people, just as there is fat and stupid people in EVERY country. America is not excused from poverty, vagrancy, nor hypocrisy. Americans do believe that America is the best country in the world, just as British think that the UK is superior.
America is one of the most geographically and linguistically diverse nations in the world. There are people from all walks of life and backgrounds. Americans know they're not perfect, no one is.
Person A : "I come from America."
Anti-American: "That's horrible. You must eat McDonalds every day."
Person A: "...Uhm no...I'm vegetarian fool. And I'm skinnier than you."
Anti-American: "....I hope you die."
Person A: "Why?!"