Canada

Environmental assessments, negotiations with First Nations, land acquisition/expropriations, not to mention that every little town along any proposed route would be pushing for a stop. Throw in assorted loons and NIMBYS and their legal efforts, and it's a wonder anything ever gets built. The fact that there are more people makes it much more difficult, not easier.

The initial transcontinental railways were very much a partnership between business and government. And a hugely corrupt one at that.

The Trans Mountain pipeline just going from Alberta to BC port is running at $30B currently. Much of that is due to opposition from locals and their legal efforts and protests. It's a hugely easier construction/engineering effort to put in a pipeline than an HSR line. Grades aren't important, a ditch is dug and the line is plopped in then covered. They're deep enough and flexible enough that most heaving won't affect it. Throw in some booster stations and Bob's-your-uncle.

HSR tracks have to be near perfect to ensure stability and there are tight limits on allowable grades/radius etc. Just the route surveys would be a huge challenge.