This is a "paradoxial" question.
The USA is not the farthest country west of Canada; in fact, you could go right across the globe and land in a place that isn't USA because you travelled west. The same goes for the east.
Unless of course, you're trying to find that country before you hit the International Date Line.
British Columbia is the Canadian province farthest West.
Denmark is the farthest east North American nation via Greenland. However, just including points on the continent, then Canada is farthest east.
Puerto Rico is the farthest east of all the West Indies countries
it depends whether you are going east or west or north or south, and where you are in the US.
Siberia is the farthest west territory. (It's also the farthest east, depending on which way matters to you)
Guatemala is the Central American country farthest to the west.
The answer is Canada but its not Russia cause then it would be the west
Norway and Iceland
The nation that is furthest west on the continent of Europe is Portugal. However, Iceland is further west but is an island. It has been traditionally part of Europe.
Canada is more narrow and stretches west to east to survive in the north south continent.
The Yukon Territory.
Barbados