She must have loved eating macaroni & cheese so much with her host family, that she wanted to bring some back to Japan to share her excitement with her own family and friends. Contrary to her expectation at seeing her friends and family crazed about it, she received a rather confused, sometimes even cold reply. No one seemed to eat it.
It was not because people expected a more valuable souvenir. Rather, it was the orangey color of the macaroni & cheese sauce. That macaroni & cheese sauce color signaled to the Japanese brain that it was extremely artificial and not suitable to eat. People asked her, "Did you eat that? Is that OK to eat?"
After I came to New York and familiarized myself with American food, I learned that even by American standards, macaroni & cheese was not exactly healthy food. The judgement of Japanese people who refused to eat the macaroni & cheese wasn't totally wrong.
Now another interesting example of a differing perspective about food. In Japan, egg yolks are more orangey than its american counterpart. This is due to Japanese people's strong preference to deeper colored egg yolks, as they believe orangey yolks are fresher than paler ones. As a matter of fact, the color of egg yolk has nothing to do with freshness. Rather, it is simply that when chickens eat red colored feed, they produce orangey yolks.
Neither of the coloring for macaroni & cheese or egg yolks harm people. And both of them are an orangey colored food. I do not know why egg yolk's orange is ok, but macaroni & cheese's orange is not ok. The only thing I can say is no matter how I may explain it, they keep believing what they believe.