Patriotism can be as deeply ingrained in people as religious beliefs. From an outsiders perspective the US seems like one of those countries where people defend it blindly like they would a religion.
I think it's important to note that, for the most part, both patriotism and religion need to be deeply ingrained in a person at a very young age for them to defend either so blindly.
US families take care of the religious aspect; US public school take care of the patriotism. If you weren't of the age where you simply don't question what you're told yet, I believe (perhaps hope?) both of these would die out in a few generations.
