There was one interesting response to the September 2012 incident in Benghazi (Libya) where Islamic terrorists attacked American diplomats, and managed to kill the U.S. ambassador mainly because there was no American military forces in the region that could reach Libya in time. A quick reaction force was created to deal with any similar incident in the future. Since 2013 the quick reaction force, consisting mostly of marines, has grown to over 2,000 personnel stationed in numerous bases (and sometimes at sea) fr0m Spain to Pakistan. Initially this force was known as SPMAGTF-CR-AF (Special Purpose Marine Air-Ground Task Force-Crisis Response-Africa). Initially it consisted of 500 marines and six V-22 tilt rotor transports in Spain. That force was expanded to 850 marines. The U.S. Navy has long maintained bases in Spain. About the same time a similar, but larger (about twice the size) SPMAGTF-CR-CC (Special Purpose Marine Air-Ground Task Force-Crisis Response-Central Command) was formed to cover similar potential emergencies further east. This force has access to more C-130s and jet fighters if needed. The new quick reaction force will be available for all manner of disasters and emergencies in Africa and throughout the Middle East (from Egypt to Pakistan). This now includes TRAP (Tactical Recovery of Aircraft and Personnel) which is ready to work with SOCOM (Special Operations Command) para-rescue teams operated by the U.S. Air Force. There is also at least one CRBN (chemical, biological, radiological and nuclear) to handle any Islamic terrorists who have got their hands on something like that. Some of the marine units on standby are at sea in amphibious ships. The basic idea is if you can get a small force of troops to a rapidly developing hot spot, you can prevent it from becoming a larger or more intense disaster.
While there are many bases the U.S. has access to in CENTCOM there is one official U.S. military base in Africa, in Djibouti. France and the United States SOCOM (Special Operations Command) have had special operations forces (commandos and special aircraft) stationed in Djibouti for years. France has had commandos there for over a decade and the U.S. moved in after September 11, 2001. The Djibouti base supports operations throughout the Sahel (the semi-desert strip between the North African desert and the Central African jungles, which stretches from the Atlantic to Somalia). The U.S. also has a number of other airports in central and southern Africa where it has agreements to quietly allow its military and contractor aircraft to operate. American warplanes (especially the very-long range F-15E) operate out of Persian Gulf air bases and have apparently carried out smart bomb attacks in Yemen, Somalia, and perhaps elsewhere in Africa. Throughout the region there are often large explosions at night. If a smart bomb was dropped from a high enough altitude, there would just be the explosion and yet another mystery no one was keen to solve.