This example was provided as an estimated upper limit - you could drive to basically the furthest-away big city within 60 hours. Other cities would be substantially less than that, because that’s an upper limit.
Driving from a small town on the western tip of NC… let’s say Franklin, NC, to Washington DC takes only 8 hours… but driving to Knoxville, TN or Atlanta, GA would only take you 2 hours.
If that drive takes you “days” by car, you might have an issue.
Or, historically, when you’re building a new factory, the first thing you do is build a rail connection right next to it