None; Mexico borders the south of the US, specifically the states of California, Arizona, New Mexico and Texas. If you mean the countries that "connect" Mexico to South America, they are collectively known as Central America, composed by Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama.
Mexico
Canada and Mexico are foreign countries that border the U.S.A. Canada is to the north and Mexico is to the south.
There are 3 countries that border Mexico: The US to the north, and Guatemala and Belize to the south.
The two countries that border the US is Canda (to the north of the US), and Mexico (to the south of the US).
South of the country, between Arizona and Texas. South of it is the US-Mexico International border.
Canada to the north and Mexico to the south. And Russia to the NW
The United States shares borders with Canada to the north and Mexico to the south. It is also close to various countries in Central America and the Caribbean. Additionally, the United States has maritime borders with Russia in the Bering Strait and with the Bahamas, Cuba, and other countries in the Atlantic and Pacific Oceans.
No. Mexico is a sovereign nation. There are treaties between the countries, but Mexico is not a protectorate.
US borders Mexico to north and Guatamala and Belize on south
When the US invaded Mexico in 1914? Yes; those where the ABC countries (Argentina, Chile, Brazil) to prevent a new US-Mexico war.
North: Canada South: Mexico
Canada in the north, and Mexico in the south.