The East Coast
Bill Bryson ends up seeing a great deal of the United States over the course of his travels, which makes sense, you know, because the Appalachian Trail stretches all the way from the Deep South to New England. That's a long walk in the woods, folks.
Hitting the Dusty Trail
A large portion of the book's action takes place on the Appalachian Trail itself, which Bryson describes it as "a vast, featureless nowhere" (1.4.1). There are even times when he gets tripped up thinking that he got turned around because everywhere looks the same. Sure, there are plenty of places that stand out along the way, but with 2,100 miles of trail to cover, those highlights make up a minuscule portion of the trip.
This lack of definition forces Bryson to focus on his internal world. He even claims that he doesn't think when he's on the trail, instead existing "in a kind of mobile Zen mode, your brain like a balloon tethered with string" (1.6.5). (Whoaaa, man.)
In our eyes, this effect is caused by two things: a) the seemingly unchanging scenery and b) the utter lack of people. Regardless, it's this emotional experience that defines Bryson's time on the AT.
Small Town, USA
Bryson gets a break for the AT in the form of the small towns littered along the trail. Bryson doesn't like the South very much, frequently deferring to hackneyed stereotypes and nightmares caused by Deliverance in his interactions with Southern folk. To be fair, though, he doesn't have many good experiences in the small towns of the South: Gatlinburg is a godforsaken tourist trap and every other town is too boring to merit mention.
In contrast, he feels way more comfortable in the North. As a quasi-Englishman recently settled in New Hampshire, it certainly makes sense that he'd find his personal values better reflected in New England.
Still, it's hard not to see his biases at work once again—he describes his beloved New Hampshire as being filled with "guys in hunting caps and pickup trucks," which would terrify him to no end if found below the Mason-Dixie line (2.17.9). But everyone is entitled to their beefs, after all, and Bryson has now seen enough of America to make up his own mind.