From one side of the country to the other.
From one side of the countryside to the other.
By a course going directly over the countryside rather than by roads.
Source: en.wiktionary.orgThere can be no two opinions as to what a highbrow is. He is the man or woman of thoroughbred intelligence who rides his mind at a gallop across country in pursuit of an idea. Virginia Woolf
I drove across country in my yellow 1970 VW bug (which I drove until 1986) to Los Angeles, having had enough cold weather in 5 years in Ann Arbor, and found a job within a few days. W. Richard Stevens
Quite possibly there's nothing as fine as a big freight train starting across country in early summer, Hardesty thought. That's when you learn that the tragedy of plants is that they have roots. Mark Helprin
After Survivor, I was driving across country and moving to San Francisco, going to get a job interning at an ad agency. And then they asked me to read for this movie. Colleen Haskell
I'll take no charity! What I get I'll earn by taking it. I would feel no pleasure it being given to me, any more than a huntsman would take pleasure being made a present of a dead fox, in place of getting a run across country after it. Lady Gregory