If the basic idea were good, it is not, your implementation is wrong. You couldnt go off cylinder count, it would have to be CCs, gross weight, and fuel mileage. The formula could take up 3000 pages and noone would read or understand it, the congress would just pass it. Also the best method of implementation would be through a $1000 'green tag' tax, and the rest in a government ran insurance plan. Insurance is already the law everywhere... its only a matter of time. Thats a better way of implementing your horrible idea.
Besides your premise is flawed. Would Jesus drive an SUV? Yes he would. That way he could comfortably fit all his disciples and gear into two vehicles not 5. In the big picture it is actually cheaper and more efficent for familys to have larger cars.
Also, Detroits bread and butter is big, profitable trucks. Your proposal would further jeapordize a distressed industry, which employs millions, to say nothing of contracting, shipping etc. Everything would be more expensive and everyone would be touched.
But in any event, who are you to influence my vehicle choice? To do so is an assualt on my rights and an affront to the One who endowed me with them.