This article is from a year ago in the New York Times, but it is still a good overview on why low gasoline prices are bad for America and the world.
For a long time I have felt the price of gasoline in the United States was way too low. Pretty much all economists believe this. Greg Mankiw blogged back in October about the many reasons why we should raise gas taxes.
The reason we need high gas taxes is that there are all sorts of costs associated with my driving that I don’t pay — someone else pays them. This is what economists call a “negative externality.” Because I don’t pay the full costs of my driving, I drive too much. Ideally, the government could correct this problem through a gas tax that aligns my own private incentive to drive with the social costs of driving.