Colombia
Step-by-step explanation:
The country that lies directly southeast of Panama is Colombia. It is the only country with which Panama actually has a border from its southern side, and it represents a point where North America and South America have a land bridge between them.
Panama is a country that is actually an isthmus between the two continents. It has an excellent location, with access to both the Caribbean Sea and the Pacific Ocean, and it also has the famous Panama Canal which connects the two.
Colombia is located in the northern part of South America. This country too has an excellent location as it is the only South American country that connects directly with North America, and it has access to both the Caribbean Sea and the Pacific Ocean.