There's any number of reasons to be proud of being an American - no other society in history has achieved the standard of living that we have. Even our poor live at a level far above what's considered to be poverty level in other countries. We're generous with aid around the globe, we're nearly always the first ones offering help and resources to literally any country that suffers natural disasters. There are so many reasons to be proud of our nation that it would be impossible to enumerate everything.
We have indeed made mistakes, but nothing so terrible or insidious that we as a nation deserve condemnation as a whole. Americans that feel shame for being an American need to pull back and reconsider their perspective. We all have a lot to be thankful for, and we as a nation deserve the credit for giving us so much for which we can give thanks.