Not sure what your point is. The US is incredibly diverse, and that diversity has very modern roots (when compared to many other diverse countries). That’s not exceptionalism, that’s just demographics. It’s not a competition. Combined with large internal migrations over its history and its large size, many Americans live in cities and regions they have no historical family connection to. So when answering a question about why “Americans seem to be very obsessed with their nationality” it seemed relevant.