The US is large enough on its own to keep petro cars running. There won't be as many advances without other markets to subsidize development, but there are enough people to keep things going. What will kill gas in the US is when there is enough charging infrastructure that people believe those 7% trips where you don't charge at home are reasonable, and so they switch their next car.

Once that happens petro will be left to things where nothing else will do. Things like farming, or heavy construction where you are using a lot more energy than batteries can supply: these are already diesel. And a few collectors, but the 1957 Chevrolet is something you only drive in parades anyway.