Even in the US, the Bill of Rights really doesn't completely cover non-citizens, so having it doesn't protect visitors. Foreign visitors OFTEN feel threatened by the US government; try listening in to what happens at the "other" immigration checkpoint if you don't believe me.
Movies that are BASED on true stories but don't show actual footage of events have room to embroider those events, and they do. They tend most often to compress months and even years of events into two hours without indicating the passage of time. Doing that makes great sense in dramatic terms because it heightens the tension, but real life normally doesn't happen with that degree of intensity, even in a war zone.
You see, I don't need to be assured that I will be perfectly safe everywhere I go, because anyone who assures me of that is lying. I can't assure anyone of that, because for all I know they could be hit by a parking shuttle bus on the way to the airport. Life is full of dangers, and I weigh the probable against the possible all the time. (I guess you would be horrified to hear that I take my kids to Northern Ireland regularly, and did even at the height of the Troubles.)
There is a high probability of danger in SOME locations within Africa, just as there is a high probability of danger in SOME locations within the US. It doesn't stop me from travelling at all; if I need to go to a dangerous place, I take the proper precautions and do so, but yes, I accept the calculated risk. I might not do it for a pleasure jaunt, but then, no one in their right mind joins the Peace Corps thinking that it's going to be a vacation. They have a purpose for being there and a job to do, and that is why they are choosing to take some risks. Professional missionaries know this well; they face danger because they feel that what they are doing is worth the risk.