I've seen more Burger Kings in my travels than McD's. The menu hardly varies in BK. I've been to them throughout the Caribbean and in London.
The best meals we had in Moscow were at TGIFriday's and at McDonalds. Just imagine eating just horrible, not to your taste food for 2 weeks and then spending 4 days in a hospital in Moscow with your sick child. When asked what you'd like to eat on the last day of the hospital stay, you remember that there is a McD's in the area. You ask if the hospital has a courier who could run for burgers for you. You'll pay whatever they want for him to do this for you. Now, imagine how good that taste of home is. Mmm... cheeseburger royale with fries and a chocolate shake. For good measure, you also buy a coke. At that point, your favorite gourmet meal wouldn't have tasted as good.
A few days later, we were staying in a hotel, our last full day in Moscow. My DH took one look at the breakfast buffet at the hotel and decided to cross the street to get McD's. He found out that they didn't serve breakfast foods there. They only served burgers and fries. He had a big mac and fries for breakfast that morning and felt the same level of comfort that I had several days earlier.
And, that, my friends, is why we often-times eat fast food when we're not in this country.... just for the taste of home.