Also, what would your counter be to the argument that ''you can streamline airport security to achieve comparable total travel times to HSR at a fraction of the cost''?
well, first I would ask for
evidence for this claim, specifically that
a) this total travel time reduction is possible in practice, on domestic routes (and for the US, not transcontinental—above a certain length the aircraft wins)—remember luggage!
b) the total cost for society per passenger•km (or passenger•mile) is actually less, door-to-door, and including a way to reckon carbon footprint, tax relief etc., and also including a suggestion on how to move the HSR passenger numbers through airports (currently, they'd be overwhelmed in countries with good HSR)
I've been flying Ryanair recently, and I've never sat this uncomfortably, nor had as little space, on a train, bus, or subway. Unfortunately, trains don't go across water, and ships are slow. (And I've rarely been this much delayed!)
HSR runs on short intervals—typically 1 hour in Germany, less in Japan—, which is possible because it can efficiently bundle passengers from different itineraries along the route, and because (unlike air travel) the overhead for an extra stop along the route is low. This adds to convenience because I can choose when to travel, and incur very little wait time. On many air travel routes, you can count yourself lucky to have one direct flight per day. For a fair comparison, figure a random starting time (say, between 8 am and 2 pm), and then determine how much later you'd arrive, choosing two major cities in Germany (or France, or Japan) as start and destination. The investment that would be necessary for aircraft to beat trains at this game (on average) would be substantial, as would be the environmental damage.