It's hard for me to imagine how big the rural Areas in America are. A plane is the most efficient transportation vehicle for those.
One time a group of friends and I drove from San Diego to Denver and back. It took 38 hours, and that was averaging 60.0 miles per hour according to hours_total/miles_total. We never left the western 1/3 of the US.
The US is large.
El Paso is closer to LA than to another city in Texas.
But all those drives are 900km or more.
It's amazing how big these states are compared to say, Colorado where I grew up.
And I don't think there is anywhere in California that isn't like a 3-4 hour drive from not California (downtown during rush hour not withstanding).
That said, if you do want to stay in California you can drive 15 hours in one direction and still be here.
And Colorado is tiny compared to Canadian provinces, most of which are at least triple its size. Want big, look at how long it takes to drive from Seattle to Anchorage.
Bad roads with bad car suspension. That would stress any beaver out.
Part of that is that the most vast vastnesses are not rural. They are wildernesses.
Humans don't live in them. And they don't have infrastructure to encourage or facilitate visitors.
In the US, you can't drive a car, ride a bicycle, fly a drone, or sail a sailboat in a designated wilderness. You can ride a horse or burro, however. But need to carry feeds free of invasive species seeds.
Then there are vast public lands where you can in theory ride a bicycle, etc. but climate and terrain make it a bad idea for most people. Much of the Mojave Desert for example (maybe search HN for "Death Valley Germans" if you want a rabbit hole to dive down).
Then there is Alaska, where airplane is the most practical and often only means of travel to and from and within.
Or to put it another way, if you thought of Siberia as part of Europe, then the scale of Europe would be more like the scale of the US. But it seems Western Europeans usually mean Western Europe when they say "Europe." And not the Balkan countries, let alone Azerbaijan.
So even from a single trailhead (end of road) you have a 1,257 sq mile circle! (Pedants would say that it's less because the road has to get inside your circle, and points on the circle would be closer to the road elsewhere.)
Very quickly places become basically unnavigable by humans even today, and even in places you'd think of as "not rural".
I'm sure there are places even in Germany where things could go missing forever.
Amusingly enough, large swaths of the "unaccessible backlands" of America is BLM land in the desert or high desert, and quite accessible to off-road vehicles, because it's basically flat dirt and so if you plow a road across it, the dirt road lasts nearly forever.
I know this story was about Idaho that has, at least today, relatively fewer places that are completely inaccessible. But if you go to Alaska, there's enough territory that's inaccessible by car that is 3x the size of all of Germany (that is, I think there's well over 1 million square kilometers of inaccessible places in Alaska).
The lower 48 is much less so, especially today. Still if you get up into the mountains, in the crazy wetland areas (parts of Florida everglades, parts of extreme north Minnesota, etc), it can get impossible to traverse by car, and very difficult by foot.
(a) most of that you can get to by car and then foot it just sucks
(b) it's not like Alaska where literally 80% of it is inaccessible