United States ... and Denmark too, because the International Boundary runs through Hans Island.
And Russian and Norway at the North Pole area.
The Country that shares the southern Border with the US is Canada.
Canada.
The country which has an exclave that shares a border with both Russia and Canada is the United States. The United States exclave which shares a border with both is the state of Alaska.
Canada and there is a maritime border with Russia.
Canada does
Washington shares a border with Canada
Canada and Mexico
The United States
Both Canada and Mexico border the US.
Two countries share a border with the United States. To the north, the US shares a border with Canada. To the south, the US shares a border with Mexico.
The country you seek is Canada.
Mexico shares its northern border with the USA.