I have been a train traveler for more than three decades. I have used extensively four networks - (one of the biggest) Indian Railway, Amtrak, Japan Rail and China Railway.
I feel the marginal improvement of 40 minutes via a new maglev line for 280KM costing $100 billion is sort of a boondoggle project...and may be a vanity project. The Shinkansen aka Bullet trains are already a costly mode of transportation, tickets frequently costing as much as a regular flight ticket. For the 40 minutes of saving in travel time what will be the hike in ticket price for a project costing $100 billion?
The other end of the equation is Indian Railway - frequently derided as slow, archaic, unsafe etc. by armchair analysts who has never set foot in a train.
A few weeks back I traveled 1800 KM, point to point on a second class ticket which took 22 hours and cost Rs 800 ~ $12 on an Indian train. The ticket was booked online, I produced only a confirmation text message (the website of Indian Railway has improved a lot and is better than AMTRAK.) The summer heat made for a roasting day, but it was safe - probably the cheapest and safest option point to point anywhere in the world. (Indian Railways are super safe compared to driving in an Indian road.)
The same travel will take may be six hours on a high speed line, but will cost $120 or more - which is what a flight ticket will cost in that sector. A majority of Indians who travel by trains will not be able to afford an extra zero in their ticket. (This is what the current proponents of high speed train travel in India ignore or do not understand.)
A version of the above exists for developing countries too...a few months back I was traveling between Washington and Philadelphia on AMTRAK. Only the wealthy - or a professional who gets reimbursed via his office - can afford an ACELA...the tickets were close to $100. Luckily there were enough "Northeast Regionals" for $40 - comfortable and faster than a Greyhound and only $10 more.
What a country like America requires is (arguably) a much more denser railway network (not as slow as the Indian network) but not necessarily a super high speed network where a majority of the population - the lower class, the lower middle class and even the middle class - is priced out. We always forget Japan Railway and China Railway has enough regular trains which are slightly slower but cheaper.
May be I am wrong...automobiles are the preferred mode of commute and the drop in oil prices means flight tickets - and driving - will stay cheaper. So the age of trains in US may be over, purely for economic reasons.