Not as big a portion of the country, but yeah coastal areas will often have a large population living in roughly a line.

In North America I believe the line connecting the most people would go from Quebec City through Montreal, Ottawa, Toronto, London, Detroit, Chicago, Milwaukee and Minneapolis (though maybe not within just 5 km of it). This is the most populous part of the Great Lakes Megalopolis and into the St. Lawrence.

Switzerland is about as big as Vermont and New Hampshire.

Could be, feel free to post a similar study on that region if you find one!