20% efficiency gains are not the same thing as no difference. If you think a 20% change is not noticeable, I would invite you to walk into a room that's 100% nitrogen.

To further extrapolate out though, that means that if the electric cars on average, are 20% more efficient that you can run five ice cars or six electric cars for the same cost of carbon.

In other words, for the same amount of global warming problems, we can run 5 billion ice cars or 6 billion electric vehicles. Neither option is great for the planet, but one option enables a billion more people to have a car while impacting all of us the same amount.

And since I don't think we're figuring out transporters anytime soon and our entire society is built upon cars...

This also discounts that if all of these electric cars were powered with more sustainable technologies like renewables and nuclear instead of fossil fuel peaker plants, they would be even more efficient somewhere between 30 and 40%. More than an ice car.