Cars came along in time to keep the streets from filling up with horse shit. Which they were doing.
Population seems to be the problem. The US had the room for all those people to spread out. In doing so, people don't like to live in high concentrations here. Therefore suburban sprawl and related problems (read cars, guns, displaced wildlife, higher costs, no time to spend with the kids because of the higher costs... and so it goes.)
Our society was too decentralized when cars were becoming popular. It will take very drastic steps to fix it. On the other paw, if we off 5 out of the 6 billion humans on the planet, it will probably make the planet last longer... I'm not feeling altruistic enough to volunteer myself. How 'bout you? :)