Tough question to answer. There have been things like "Manifest Destiny" that encouraged Americans to feel empowered and blessed by "God." And beginning in the 40s and 50s Hollywood, in conjunction with our government began making films that were ostensibly entertainment but contained much propaganda. That had a profound effect.
Me... I think America is special because as some of our our founders intended/believed, it is an experiment in government. There has never been a government quite like it.
Right now that experiment is in crisis and in danger of failing. I don't mean the nation is in danger of failing... just the ideals. There are people who want to inject religious laws and themes into our government. There are people who are just as adamant in their opposition to that.
It's very iffy at this point.
There are also those who confuse patriotism with nationalism.