Drop a raindrop anywhere in the world and watch where it ends up
It appears that the US/Canada border is closed to water o or virtual flyovers. Selecting a location in NW Montana flys you right over multiple mountain ranges. It took me a minute to realize that the incorrect, straight line portion of the path starts where the river flows back into Canada. The strict no fly zone means it has to fly along the border until the river returns to the US.