Why does it make sense to have high speed rail between Paris and London, but not between similarly distant New York and Philadelphia?
Because Philadelphia isn't Paris.
Why can't we put a loop going from Chicago to Detroit to Cleveland to New York?
Because the cities are 1) not as populous and 2) farther apart than the capitals of Europe.
Or connecting Miami, Tampa, Orlando, and Jacksonville? What about winding from San Diego to San Francisco?
It may not be economical to make links between the coasts, or over much of the Midwest. But the areas I'm talking about are areas with European density, with urban cores at reasonable distances from each other. Believing that the United States as a whole faces "distances that dwarf that of Europe" is downright Texan.
And so you are claiming that distance and population density doesn't matter?
The US has a third the population density. And to boot, there are three major disconnected population centers with distances over 1500 miles separating them. No such situation is present in Europe to *any* degree.
There is simply no comparison between the US and Europe for rail travel. None. And yet certain types of people lay their ridiculous guilt trip on the US for not embracing rail, without even considering that.