I don't recall making it too clear that many Americans are taught about their nationalities, because it's true that many are not--many people go on with life and use "nationality" once in a while to get some meaning or fun out of it. Not to mention, many blacks in America don't know their lineage simply due to it being cut off at a certain point in time. But basically, lots of people do not care much for nationalities and when you ask them, they simply tell you "white American" (it's doesn't take long to realize that many Asians are familiar with their nationalities and are much associated thanks to parenting with their culture and heritage), because they know no better. And if they HAVE to say one, it becomes "English" because again, they know no better and "they guess their English" just because it's the language they speak and that the original western civilization starters here were the British.
I agree with you that being "proud" of one's nationality(ies) gives people a sense of meaning to their otherwise rather meaningless lives. The pride that I was talking about really applies to people who are significantly attached to their heritages. The Colombians who tell you that the best beaches are in Colombia and refuse to believe that Colombia has the highest murder rate in the world, or the Russians who truly believe that Russia is the greatest country in the world and that everyone is under the mercy of "Mother Russia", and that they have the best military in the world, etc. They are blind followers with closed minds and a provoked bias. So, I was making the point of pride when it comes to one's heritage altogether.
At the same time, it bothers me when my American peers don't even know or care about what nationality(ies) they are, as they are too busy tending to other "needs". When it comes to being American and ethnocentrism kicks in, many of these people are proud. Those who aren't so proud about being anything are rare and almost always lead lives that simply satisfy their desires. That is, a very routine one where religion also plays little to no role in it, and one just eats, sleeps, defecates, and takes care of their "fun factor".
Well anyways, I found this video of one of the best and modern comedians I have ever heard, George Carlin, who is extremely realistic in most of his views. He does a GREAT job explaining this concept and makes for a grand comedian.