Bill Maher rant on America's biggest problem.
Stupidity. It's the world's biggest problem as well. It's not simply a problem related to ignorance, but an actual inability to learn, use logic, reason, and critical thinking.
25% of Americans have an IQ of 89, or lower. There is a direct correlation between IQ, and education, and a correlation between education, and religiosity. Coincidentally 25% of Americans are categorized as Christian fundamentalists. 40% reject evolution, 35-40% think global warming is either a hoax, or something we don't need to worry about.