> If you count about 140 mph as high speed train, Finland (pop. density 17/km^2) and Sweden (22/km^2) seem to be doing just fine.
Citing the population density of Finland and Sweden as a whole is pretty disingenuous. Those two countries have densely populated urban centers in the south with high speed rail yet vast sparsely populated areas in the north with nothing. High speed rail gets built where it makes sense and no amount of hand waving is going to make building a high speed rail line from LA to Chicago or New York viable. With that said, I will agree that politics and culture are certainly factors.