Re: ...there.
"For one thing, a national high-speed rail system is a bit easier if your whole nation is smaller than Montana."
Check out Eurorail some time.
"And, apparently only two high speed rail routes in the entire world actually turn a profit:"
Does our interstate highway system turn a profit? Are you willing to do without it?
This is just a replay of "Why should I pay to educate other people's kids? Let's do away with property tax." Been there, done that, and lost one of the best primary education systems in the nation.
Transportation (like education) is good for commerce, along with a number of other things it is good for. If it can't be done profitably, and it is deemed desirable, then it is something the government should get involved in.