Our cities and country are really not set up to make it worthwhile....one reason why we invented the airplane.
Europe, Japan, both are relatively small, composed of dense cities that basically were created pre-car and are thus small, and usually have subways.
Its not the intercity speed that inhibits HSR, its the "well, how do I get from the train station to where I'm going" that is the problem.
Sure, you can have rental cars, uber, zip car, etc, but then why not just take a plane?