Understand your point about less advantaged people but that would probably be a typical American problem at the moment. As you said that is part of your culture and you'll have to face a huge infrastructure problem. However, the most famous American car in history remained the "Ford T" and that is far from being big.
Europeans tend to use smaller car as we have less free space to drive them may be. That's also why I prefer to do better with existing technologies. It is cheaper to make more effecient fuel engines that to make brand new engines using the best improvement we can think of.
In France, for now, when you buy less consuming vehicles you get a 700€ to 1200€ (the second bonus remain a dream to these days) bonus from the state (roughly 1000$ to 1600$) + an average constructor bonus of 2000€. That makes people think. You also can sell your older models for a guaranted price: I sold my wife 20 years old city car for 2500-3000€ (constructor bonus included; hey they are not crazy).
Moreover, they are curently taking out several cars that will cost you less than 9000€. Still a big investment but affordable by more people. Of course they are not the less consuming ones and the most fancy cars but they are now very decent for that price with plenty of room for the family. The Funny thing is that these car were first bought by wealthy people (guess why
). Nevertheless, one of my neighbour, who happen to be one of the poorest familly around, just bought one going from a near ruin to a decent vehicle. They are nice people and I was truly happy for them.
A side advantage is that they don't rely on much electronics and would work in T2K.
Here is the most popular model at the moment in France: the Logan MCV.