1) HSR needs to travel at a multiple of the speed of highway traffic to be considered HSR by most people, I suspect. If a HSR train travelled down the median of a highway and the trains travelled at the same speed as traffic (60-80 MPH), what's the benefit (aside from reduced carbon), and you travel to/from train stations (not your driveway) and on the HSR train's schedule (not whenever you want)...
2) The issue isn't the land between cities, it's the land near the cities - If I'm running a train from Chicago to Denver, for example, there's very little "public land" the Gov't could just give HSR lines, and if you have to put the HSR station 20 miles outside downtown Denver of Chicago, that alone becomes a barrier to access (sure add a bus/light rail line, but that only slightly impacts the issue of access from anywhere inside Denver of Chicago, for example).