Rural areas make up very little of the population. Although there's some improvement there--I live in a rural town that's quite navigable by bicycle and has a good bus system.
Uhm, there are no buses here (see other posts) and bicycles don't work in certain conditions (high winds, snow, -40F below weather). Plus, let's also remember that a lot of places don't have facilities for people to bike into work (like showers), not to mention the people who can't use bikes.
So what? We live in the sticks. There aren't enough of us to matter. If we keep driving around with one SUV per person it doesn't add up to much, comparatively. The low hanging fruit is fixing the metropolitan areas. Most people live there, and demographically, people are still moving there. So fucking around with making cars and rural areas more efficient isn't going to make much difference compared to making metropolitan areas more efficient and reducing car usage within them.
That said, rural college towns can have pretty awesome bus systems that run all year, even during subzero temperatures, and they can also have bike paths that go mostly everywhere, which are usable for nine months of the year. Because mine has all that. I'm sorry yours doesn't; but obviously, there is room for improvement, which is exactly my point.
The real problem is the suburbs.