All that said, though, the problem of route density is a real one here in the US.
Europe is much more densely populated, and very few cities are more than, say, half an hour or an hour away from a high-speed rail line. It makes it easier to run efficient feeders to the backbone networks.
And even in Egypt (the original subject here), I think this can be made to work, because the population is concentrated in a "T"-shaped region (Alexandria down to Luxor, and the Mediterranean coast, and it will be much easier to set up a few lines that can serve well over 50% of the population with very little feeder support needed.
On the other hand, in the US, for example, you'd need to set up an extensive network of feeder lines just to get to the main routes (even if you laid down high-speed routes along the same pattern as interstates). If it takes you 2 hours to drive to the nearest high-speed station, a 5-hour journey on the train itself, and then have to find yourself a one-hour ride to your destination, that puts a damper on its utility, especially if you can get a couple of flights that will do the same distance in 3 or 4 hours, even including the security theater involved.