Country miles are much, much longer than city miles. Or they are if common usage of the expression country mile
is to be believed. Kind of like the old "which is heavier - a pound of
lead or a pound of feathers" deal. Why are country miles longer? I
guess they're longer in the sense that there's just more of them.
Everything out in the country is just so far away from everything else.
This is multiplied by the fact that the exprience of traversing country
miles is an experience characterized by tedium.
The effectiveness of the expression, and the reason for its
popularity I think, is in the romanticism in the metaphor:
conjuring images of long, featureless stretches of back road,
five-house hamlets, insular filling stations, and barn-like
churches. The romantic nature of the metaphor works well in songs
like "Country Mile" by Camera Obscura ("I won't be seeing you for a
long while/And I hope it's not as long as these country miles/I feel
lost...") and "Miserable Lie" by The Smiths (which ends with a
forceful repetition of the line "I'm just a country mile behind the
world" in Morrissey's stunning falsetto).
I am painfully familiar with the length of country miles. Ithaca,
New York, which I call home these days, is about a hundred country
miles from anywhere else interesting. It is surrounded by a sea of
nothing. Nay, it is surround by a sea of fire that will burn
your soul. (dear Central New York reader -- of course I wasn't
talking about your town). Ithaca itself is great, but its
insularity means no spontaneous road trips to some interesting
near-by spot. It means you can go to the City once in a while, but
it's something that requires planning, and in the mean time, Ithaca is
it. Since everywhere I want to go is in Ithaca, it's not too bad, I can
get everywhere either on foot or on bicycle. But if the things in
Ithaca were spread out across the Ithaca area, I can see how I would
very quickly get incredibly sick of these country miles.