He could have written this story in a version of the US, but he picked a bunch of non-American cultural markers that suggest the setting should be very unfriendly to cars, and then doesn't address it, and his whole attitude towards it is just making me cool towards the book.

I don't blame you. I suspect he started the whole thing with a very flip attitude and little experience with the genre -- otherwise he would have realized a long time ago the problem with casual asides in a wholly created world. There are plenty of fanfics with 11 page documents to keep things straight.