Why do so many U.S. citizens say they're visiting "Africa", instead of specifying the country they're visitin?

Sadly, there are indeed some Americans that could not find the DRC on a map of the DRC itself. One asked me about my accent once and I told them I was Nordic and they wanted to know "where is Nordic?" It is much easier to simply assume the person has very little or even no knowledge of the world outside their borders (as a lot of Americans do not) and say "Africa". I've actually seen on this very site, on a regular basis even, people who seem to believe Africa is a country rather than a continent with many countries. One accused me of "lying" when I told them that Egypt was in the North of Africa. I do not think they teach geography in this country at all.