U.S. - Slovenia, 2-2 tie.

United States: 310 million people (and apparently 400,000 census workers)
Slovenia: 2 million people (smallest nation to make the World Cup).

Final Score: 2-2 (and, yes, it was controversial).

Just think of how good Slovenia might be if they had, say, 10 million people and the U.S. had only 300 million?