And how did this existing network of iPhone users come to be if it was just about fitting in? This is obviously flawed logic.
Why even talk about other markets unless you can control for all of the other variables? The other markets are completely different, there is no market like the US market just like there is no market like the market seen in China or India...or maybe if you think as you do, you should ask the question why teenagers in the US market are more likely to try to "fit in" than other teenagers in other markets...
I mean it's probably a combination of two: iPhones are generally considered better (and I concur with this sentiment) which leads to initial adoption and then everyone else has to have one too.
I mean he'll I'm an adult supposedly and am as susceptible to trends/fashions/being cool as anyone else.
So either American teens are very discerning of UIs, or they just try to fit in within a network of existing iPhone users.