High speed roads would offer much more utility, and would allow the freedom of movement that we Americans want.
Imagine, hopping in the car at 8 AM in Nashville, TN, and being 600 miles away, in Jacksonville, FL in 3 hours or so. While still having your car, and your sidearm if you choose to carry. And anything else you want to carry with you.
Frankly I would much rather taxpayers funded the research of genious level engineers than pay for faster choo choo trains!