I think a lot more goes into making urban life better for the environment than just cars. Off the top of my head I would expect the following to contribute:
Suburban heating and cooling involves larger spaces for less people (houses being bigger in the suburbs),
In an urban environment, there is a lower environmental cost for transportation and processing of food/water/other goods (fewer locations to deliver to).
In an urban environment, I would expect fewer materials are needed to maintain infrastructure (power lines, water pipes, roads, etc). Manufacturing all of these parts involves an environmental cost.
Suburban living currently almost certainly means a big lawn. Traditional green lawns are bad for the environment.
Urban communities can also centralize waste disposal and (I suspect) more easily implement recycling programs.
Finally, don't forget that an electric car is only actually better for the environment if the electricity is produced sustainably (this is mostly not the case in the US). I suspect that electric cars may actually be worse for the environment if powered by most US power plants.
Suburban heating and cooling involves larger spaces for less people (houses being bigger in the suburbs),
In an urban environment, there is a lower environmental cost for transportation and processing of food/water/other goods (fewer locations to deliver to).
In an urban environment, I would expect fewer materials are needed to maintain infrastructure (power lines, water pipes, roads, etc). Manufacturing all of these parts involves an environmental cost.
Suburban living currently almost certainly means a big lawn. Traditional green lawns are bad for the environment.
Urban communities can also centralize waste disposal and (I suspect) more easily implement recycling programs.
Finally, don't forget that an electric car is only actually better for the environment if the electricity is produced sustainably (this is mostly not the case in the US). I suspect that electric cars may actually be worse for the environment if powered by most US power plants.