North America and South America share a land border with the United States.
The two continents that border the Black Sea are Asia and Europe. The Black Sea is wedged in between these two continents.
The United States of America is bordered by two countries, not continents: Canada and Mexico. To the west of Alaska is Asia, however, not being landlocked, one does not say that they border eachother.
Istanbul
The longest land border between any two continents is between Asia and Africa, specifically at the border shared by Egypt and Israel. This border separates the African continent from the Asian continent at the Sinai Peninsula region.
Nothing is between the two continents, as they border.
North and South America
Only two continents border the Red Sea, they are Asia and Africa.
The two continents are Europe and Africa.
border
No continents border Antarctica. The continent is surrounded by the Southern Ocean.
Two continents that lie west of the US are Asia and Australia.