The trick is, train isn't cheaper that planes. Ecologically, the French TGV isn't considered better than planes in terms of glasshouse gases (i.e. the ecological approach says a km travelled is bad, whether by flight or by train). Moneywise, it mostly depends on how you expropriate land owners. Europe is really good at citing the "public good" or "strategic interest of the nation" to reclaim private land, and I'm saying that because I've seen that the indemnification is way below the market value of the fields. Whereas in US, litigation is costly and land owners can be very powerful, making the costs soar for train infrastructure.

I'd like to see a study thay analyses whether tge whole train-in-Europe vs airports-in-USA might even be explained by this sole ability of US landowners to defend themselves.

However, remains one question: If Europeans can travel by train without being searched, isn't the USA violating the freedom of movement by using planes instead of trains, then imposing the TSA and other no-fly-list laws?