Higher density indeed tends to be more resource efficient. The problem is much of what is called a "big city" in the US is a sprawl of low-density suburbs that,

Higher density indeed tends to be more resource efficient. The problem is much of what is called a "big city" in the US is a sprawl of low-density suburbs that, due to their city planning, require more driving to get to anything than, say, if you lived in a small town.