This argument doesn't hold water. Why is there no decent regional train system in the US then? Your point explains why there is no coast to coast NYC-SF bullet train, fair enough. Each US megaregion [0] could have a decent train system like France, Germany or Japan.
The short answer is that not enough people want that. The argument seems to be that they would if only they knew how awesome it was. But that argument isn't sticking, so the political will to make it happen is not there.
It seems a bit more complicated than that to me. In many cases Americans in at least some regions do want it, and even vote to fund it, but nonetheless the political & civil service machinery seems unable to actually deliver it. Especially, unable to deliver it for anything approximating a reasonable cost. See, for example, the way over budget and delayed NYC 2nd Ave Subway, or the California HSR. Some countries are able to build a single 400-mile HSR line in less than 30 years.
I take the Acela from Boston to NYC often. It's okay but not great. Nothing like the TGV which I've also ridden.
If the trip could be two hours instead of 3.5+ that would be great but as it is it is barely justifiable over flight (being dropped off midtown is a big bonus tho).
The benefits for even longer travel just don't exist. Once you start getting into the 4+ hours on a train it's almost always better to find a flight.
Japan's shinkansen travels at 2-2.5x the speed of the Acela. At the maximum speed of current bullet train technology, Boston - NY could likely be done in about 1.5 hours, Boston to Washington in about 2-3, and even Boston to Cleveland in around 3-4. That basically covers the entirety of travel in the Northeast corridor.
This doesn't even cover the new maglev trains that are expected to go into service sometime in the late 2020s in Japan, which have a maximum speed of 550km/h, expanding the range of that 4 hour "maximum" significantly.
The major problem with the Acela is that it mainly runs on older infrastructure that wasn't designed with HS trains in mind. This severely limits its speed on most of its route. Most HS systems in other places around the world are on newly developed HS lines that were built up specifically to support the much faster speeds and requirements of these trains, and are completely separate from the regular rail lines (which might be running in parallel nearby).
It is also that many people actively oppose trains because they are afraid that the trains will bring in undesirable people (poor people, criminals, hipsters from New York) to their neighborhood. When New York MTA tried to extend Metro North service 25 miles beyond Poughkeepsie on already existing tracks, residents of the surrounding towns opposed the extension claiming that NYC commuters will move to their rural towns.
The original is from John Bartholomew and co. from the Edinburgh Geographical Institute. It was published in 1914 in the Atlas of economic geography by Oxford University Press.
https://archive.org/details/atlasofeconomicg00bart/page/n93
It is similar, but Hill Climbing moves one parameter at a time. While gradient descent moves along the steepest gradient adjusting multiple parameters at a time, but it requires the function to be differentiable
Half of the problem with cars is a geometric one, they take up too much space. They give rise to sprawl and thus increase the demand for cars in a vicious cycle. Them being electric or self driving will not solve that.
[0] https://en.wikipedia.org/wiki/Megaregions_of_the_United_Stat...