The answer will vary, depending what country you live in.
Canada!
Minnesota only forms a border for one country: Canada.
Russia forms much of China's northern border. The two countries share a long boundary in the north, primarily in the regions of Siberia and Manchuria.
California's southern border is shared with the country of Mexico.
Canada forms the most northerly border of the U.S.
The country of Mexico is north of Guatemala.
The country of Mexico is north of Guatemala.
The country of Mexico is north of Guatemala.
The country of Mexico is north of Guatemala.
The country of Mexico is north of Guatemala.
Canada does,
The country that forms most of the northern border of the United States is Canada. The country directly to the south is Mexico.