Inspiring! I have similar thoughts about my home and native land, Canada.
Also, it's practical in an important sense. From the purely cynical blood-and-guts perspective: when an Empire is growing, the best citizenship to have is the Empire's. I know the foregoing sounds amoral, but we sometimes have to consider the practical side. Consider the advantages a Briton enjoyed in the 19th century, or the advantage enjoyed by St. Paul because he was a Roman citizen.
And you are right in that Americans are most familiar with the idea of Liberty. That definitely counts. Why count on (say) Mexicans or mainland Chinese to discover the ideal of Liberty when so many Americans already know it?
In my case, I'm sticking with my home and native land for a more quotidian reason: I know how the system works in Canada. That's good enough reason for this Canuck to stay put :)