I think people will still want to have their own cars — having to unload EVERYTHING from a shared car that you’ll likely never see again every time you’re done with it would be really annoying. A lot of women I know use a car essentially as a second handbag.
Plus Americans are prissy and don’t want to share seats that have been sat in by others repeatedly. Rental cars get NASTY after about 30,000 miles.
I wouldn’t say that LEDs would cut energy usage drastically. Lighting is only about 10-15% of energy use in the US. LEDs use about 1/5 the power as incandescents, so the cut will be 12% if we’re lucky. And that’s not taking into account fluorescent fixtures that are already installed as well as increased electric heat usage in winter.