If you're willing to be a little more flexible with the definition of a country, many U.S. states and Canadian provinces look fairly easy to cross in a straight

If you're willing to be a little more flexible with the definition of a country, many U.S. states and Canadian provinces look fairly easy to cross in a straight line. They contain long, straight stretches of roads, and even their borders are straight lines. You might as well just walk or drive along the fence.