Final answer:
Panama is the isthmus country that links Central and South America, famous for the Panama Canal.
Step-by-step explanation:
The country that is an isthmus linking Central and South America is Panama. The Isthmus of Panama serves as a land bridge between the two continents and is the narrowest point between the Caribbean Sea and the Pacific Ocean. Panama became an independent nation from Colombia in 1903 with the aid of the United States, largely due to the strategic importance of building the Panama Canal, which was completed between 1904 and 1914 and connects the Atlantic and Pacific Oceans.