From a recent survey:
When Americans were asked if they think the United States is the greatest country in the world, there were sharp differences in the responses across generations. In total, 48% of Americans believe the United States is the greatest country in the world and 42% believe it is one of the greatest countries in the world, but a significant portion of the Millennial generation responded differently.
Just 32% of Millennials believe the U.S. is the greatest country in the world. That number progressively increases among the Gen X (48%), Boomer (50%) and Silent generations (64%). Millennials were also the most likely generation to say America is not the greatest country in the world (11%).
Millennials also are less likely than their elders to express patriotism. A majority of Millennials (70%) agreed with the statement “I am very patriotic.” But even larger percentages of Gen Xers (86%), Boomers (91%) and Silents (90%) said the same. This generational gap is consistent and has been identified in surveys dating back to 2003.
The annoying 'generation' names can be ignored -- the key thing is that the younger an American you are, the less likely you are to call yourself 'patriotic', which (if you'll pardon a bit of snark) describes the mental state Americans denounce as 'nationalistic' whenever non-Americans display it. In related news, the number of non-religious Americans is on the increase -- about 20% of Americans now fits this category.
Sociologists have long puzzled over the U.S.: given its levels of prosperity, technological advancement, and education, it should be a lot less religious and nationalistic than it is. Put crudely, the richer a country gets, the less religion it needs, and the the more educated its citizenry, the less prevalent the cruder forms of nationalism and tribalism. We seem to be seeing a gradual end to this aspect of American exceptionalism: in 20 years, the psychological profile of the average American will probably be much closer to the average European, Canadian, or Japanese.
I would be willing to wager the Internet has had something to do with this, but that's pure speculation. So here goes: If you seek critiques of religious faith, all manner of them -- from the ridiculous to the cogent to the sublime -- are no more than a mouseclick away. It's hard to enforce conservative sexual mores in the age of Internet porn, where any anyone can see people having loads of fun with their genitals, and afterward suffering no disease, ostracism, or scorn at all. As for the nationalism angle, you can hardly swing a dead cat in cyberspace without hitting a website that shows you that many people (1) distrust the U.S., and have legitimate reasons for doing so (yet who aren't anti-American cranks); and (2) don't consider the U.S. paradise on earth, and think the quality of life they enjoy in their own country superior to that of the U.S. It's a bit hard to maintain the fantasies of your country's superiority and innocence in the face of these competing narratives.