Canada is unequivocally the northernmost country in North America. Its territory extends from the Atlantic Ocean (east) to the Pacific Ocean (west) and from the United States border (south, 49th parallel + Great Lakes/St. Lawrence) to the Arctic Ocean (north), encompassing the North Magnetic Pole and the northern tip of Ellesmere Island (83°N latitude)—the closest land to the North Pole outside Greenland.
The U.S. (Alaska) reaches 71°N (Point Barrow). Greenland (Kingdom of Denmark) extends further north (83.6°N at Cape Morris Jesup) but is an autonomous territory, not a sovereign country. Thus, Canada holds the title for sovereign nations.