Why is the USA so proud of itself and its flag?

I'm from the UK, and have lived in France for a number of years as well. Britain, if anything, is, historically speaking, a more accomplished country and therefore has more to be proud of than America, a country that from the outside world seems to have a ruthless, crude and hypocritical society (thanks to the international shames of Guantanamo Bay, the War on Terror, the Iraq War, George Bush, pollution and global warming, racism, segregation, ruthless warfare etc). In the USA it is common to show the flag in clrooms etc, yet in Britain, it's really uncommon fly a Union Jack anywhere. So why does America seem to be so cringingly proud of its stars and stripes?