Leave aside whether McD is mediocre food or not, but what makes it any more a cultural icon of triumphant American capitalism over local tastes and cultures than, say, Miles Davis, other than that some people here prefer Miles Davis to Yanni and think he makes better music?
The popularity of McDonald's in Russia, at least, has nothing to do with triumphant US capitalism trumping Russian culture. It is because a Big Mac costs only 40 rubles and the food has reasonable quality controls on it, unlike something you buy at a kiosk, which might contain dog meat for all you know. Also, they sell Russian-style potatoes and pirozhki.
Chris Doss The Russia Journal