Mexico
The closest place to the southern US border is Mexico, which happens to be in North America, just like the US is. The continent that borders North America is South America.
Mexico!!!! There is a common international border between the two nations.
Border? It is on the southern US border.
Florida
The Country that shares the southern Border with the US is Canada.
Mexico is the southern country that is the closest neighbor to the United States. Mexico has a border with the United States that has a total length of 1954 miles.The country is Mexico.
russia is the closest country and it does not touch the border of the US!!! :)
The closest southern neighbor would be Mexico.
The US state of South Dakota is the southern border of North Dakota.
Rio Grande forms the Southern border of the United states.
The U.S. southern border is formed by Mexico and the Gulf of Mexico.