I mean, the NY transit system will take you pretty much anywhere in an area with a population of 8M. For scale, note that New York State alone is about 4x larger than Taiwan. I agree that having walkable cities is a good thing but it's not like all of the US is one giant suburb, and it's not like the US has anywhere near the density that would be required to justify "high speed rail across the whole country, just an hour away"