Final answer:
The principal guerrilla organization in Colombia was the FARC, controlling extensive territories and being involved in various illicit activities to fund their insurgency. Recognized by some neighbors but not by the U.S., they played a significant role in Colombia's internal conflicts.
Step-by-step explanation:
The major Colombian guerrilla organization was the FARC (Revolutionary Armed Forces of Colombia), which has been known for drug sales, kidnappings, and extortion to finance its operations. FARC was once a dominant force, controlling regions as large as U.S. states and functioning as a sizeable military and political entity. Although FARC is recognized as a political entity by some neighboring countries, the United States and other nations in the region have not extended the same recognition.
Insurgent groups, including the FARC, have had a substantial impact on Colombia, influencing its politics, society, and the stability of its government. The U.S., being the biggest consumer of Colombian oil, has a vested interest in ensuring the stability of the country. The complex relationship between guerrilla organizations, the government, and drug cartels paints a complicated picture of the political landscape in Colombia.