Hmmm, I think you might actually be right, in terms of how long it takes to replace all existing cars. In the US, it looks like the average passenger car is 11

Hmmm, I think you might actually be right, in terms of how long it takes to replace all existing cars. In the US, it looks like the average passenger car is 11.6 years old. Since that's the average, even optimistically, there are probably a LOT of 15+ year old cars on the road. So you probably need to have all new cars sold in the US be electric within 5 years to have a more-or-less complete turnover within 20 years. (The figures for non-pickup trucks are even worse, with 17 years being the AVERAGE.)