Stupidity or Ignorance?

So, in addition to attending grad school, I also work at a pleasant little retail shop. I enjoy it quite a bit - it's nice to have such a concrete job, for a change. I know what I need to do, my tasks are clear, I get them done, and I see the results right away. Very different from social work, and very refreshing. I leave at the end of the day, and I leave my work there. I don't go home worrying about my clients, because I don't care about them.

The store is a factory outlet store located in an out-of-the-way neighborhood, so it's kind of a "destination" shop for people (unlike a store in the mall). The company is based here in Portland, and their product is known all over the world. So, we get lots of customers from different countries. The other day, a French couple and their adult daughter came in. Anyone who knows me knows that I am a total French nerd. I love the language and miss speaking it. I followed these people around the store, eavesdropping on their conversation and grinning. One of my coworkers told me I should talk to them, but I was too embarassed. However, I found the courage to converse with them while ringing up their purchases, and we chatted for about 10 minutes in French. I was glowing, because I really love speaking French, and I miss it terribly. After they left the store, one of the managers (a lovely 23-year-old woman who I really like) and I had the following conversation:

Her: Wow. That's so cool. You're like, so worldly.
Me: Well, not really. I mean, I just studied French for 10 years in school, so it's easy for me to remember. I also used to work at a French language camp and I studied abroad in a French-speaking country, so that helps, too. But, I don't think that makes me worldly.
Her: What country did you go to?
Me: Cameroon. It's in West Africa.
Her: Oh, cool. So, is that the same as South Africa?
Me: No. South Africa is in southern Africa, and they speak English there.
Her: Huh?
Me: See, a lot of western and central Africa was colonized by France and Belgium, so many of the countries in that part of Africa speak French. A lot of southern and eastern Africa was colonized by the British, so many of those countries speak English.
Her: But, isn't British the same as French?
Me: No. The British people come from England, so they speak English. French people come from, well, France, so they speak French. Make sense?
Her: Sort of. But, I mean, is the English they speak in England the same as the English we speak here?
Me: Yes. See, the U.S. was also colonized by the British, so we speak English here, too.
Her: Wait, I'm confused.
Me: English people came over to the U.S. and made settlements, so that's why we speak English here. I mean, we have a different accent, and we use some different slang words, but it's still the same language.
Her: Oh. Huh. Interesting.

This woman has a bachelor's degree from a 4-year university!!!! How does someone not know that we speak the same language as the British? Or that British and French aren't the same language? And, how does someone not understand that the U.S. was colonized by the British? I didn't want to confuse her even more by mentioning that we were also colonized by the German and the Dutch, or that there are hundreds of ethnic languages that are also spoken in Africa. I am just amazed at how....unknowledgeable some people are. I mean, really. This is basic, basic, stuff, right?