A flat map would suggest...... True it does.
as the real earth is a sphere a transpolar route could .... Be shorter, could be over an area not covered by Air Traffic Control, have alternate runways to use in case of emergency, have rescue services nearby....
International flights have been using Polar routes since World War TWO.
You can easily get a flat polar projection map to see this.
On line google map will show the route.
Just south of Iceland, over Greenland, Canada ( Nunavut Territory,Saskatchewan, Alberta, British Columbia)
Washington State for Seattle.
For a California destination the route over Canada would be over Manitoba
Google maps measure distance function a right click shows you all the routes you care to look for.
ATC decides the exact route taking into account other Air traffic, weather and other stuff.
In the old days when planes could not fly as far. The route was strait line from London to Gander Newfoundland for a refuelling stop, To reach the west coast of North America would usually require one more fuel stop along the way.