Well, I can assure you that if train ridership increases, the risk will increase as a function of the attack vector and the threat by muslims. As that risk profile increases, so will the "security nonsense" and difficulty getting there increase.
Also, the degree of expedience at which airports function leaves a lot of room for improvement. There is really little reason why it could not get far more efficient. You seem to also miss the fact that even if you establish a route through 1,000 miles of other people's land and have dispossessed them through eminent domain, and you have blasted your way through ecosystems, you are then stuck with specific routes that can only adapt by scaling throughput of that specific route.
Think of it this way, with the pestilence of douchebags overrunning Austin there is no way that rail could have accommodated that growth, let alone even triggered it. What, are you going to build high speed rail infrastructure across multiple states to California to accommodate the flow of douchebags to SXSW and ACL? You'd be lucky to be done before Austin has suffocated itself and the bubble bursts and the next fad has drawn the attention of the pretentious class.
I won't disagree that train travel is more comfortable, but hell, you really need to be because the trip, at best, is going to take you three times as long. Because what you are also missing is that we are talking about high speed rail here, we are not talking about fast rail like Acela, which is quite convenient in the NE corridor, but also only because of the population density. But even that train stops on a regular basis, which is also a function of what makes is even remotely not a horrific idea even though it still loses money. The problem with air travel these days is that the Airline industry has essentially captured regulators and legislators and are raping the public with high prices they are colluding on and ever decreasing service and features, also essentially due to collusion and a lack of real competition.
Don't get me wrong, I realize that train travel has some benefits and is probably more energy efficient and less polluting, but reality is that it is in no way cost effective let alone adaptable and flexible.
The thing that kind of irks me the most about he wide eyed, pie in the sky, rail supporters is that they have absolutely no idea how much it actually costs to provide the kind of level of rail and public transportation infrastructure that you see in Europe. The costs are astronomical both in long term investments and in M&O. There are inklings of how much it really costs, but reality is that no one really have an accurate understanding of its cost because European governments keep that information under lock and key, lest the rabble find out how much their money is squandered.