Given US sprawl development, this is almost entirely relevant to suburban rather than rural populations. A majority of the population is suburban, so its not a minor point (!), but my focus here was on serving rural populations in the face of Peak Oil, so I did not look at that.

Intercity networks, though, intrinsically serve rural counties, because the optimal spacing of stations and normal population distribution in the majority of the US (that is, outside the Northeast Corridor) dictates that, eg, a small city like Coshocton should get a station on a Regional HSR corridor between Pittsburgh and Columbus, which means far superior accessibility to rural areas in that and the neighboring counties than airports can ever provide.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.