My own anecdote on the topic is this: When I was in the States a few years back, Knott's Berry Farm, a theme park, did not open its doors until the national anthem was played. During this event, I gathered that such a thing was almost innocuous to the Americans around me - which as a Kiwi, it was pretty weird on its own. It had already been a very weird month as the USA is a land of horror and fantasy that I will never truly grasp. But what really sticks out to me is one particular kid, maybe no more than two or so years old, being forced into the hands on heart position by his mother despite clearly having no idea what was going on, and the mother getting a little shitty when the kid didn't want to do so. The German tourists that I was hanging out with were equally bemused by all this. Once it ended, I couldn't help but be a nosy tourist and just ask the mother if these sorts of openings were common, or something to that effect. She said 'Nah, but they should be. This is America!" and went on her way. This was 2012 so it wasn't all that long ago on a cultural level - I thought it was weird then, and I think it's weird now.
But the relevance of that story is that despite it being weird to me, it was entirely optional and a decision on part of a business to connect with the nationalist spirit, because nothing connects with American consumers wanting to experience a family day than blaring that tuneless piece of white noise. It's weird, but it can be argued to be part of America's notoriously strong sense of patriotism. That's me having good faith. I'd call America a nationalist hellhole, personally. Where it goes beyond a weird conditioning of patriotism and into the nationalist brainwashing category people here have mentioned is the Pledge of Allegiance - it and in itself is something I find rather abhorrent, this idea of pledging allegiance to ideals that have constantly been betrayed, ideals used to justify the oppression and denial across the spectrum of most within American society, let alone America's policies across the world. Let alone the concept of fealty to both a physical flag (as is seen in laughable news stories where students stand in pouring rain to make sure a broken flag doesn't touch the ground) and undying nationalism to the country said flag represents. But to enforce it within the education system from the moment kids can walk and talk? It is vile - to treat kids like little more than puppets for ideology is just... fucked up. It is unquestionably creepy. It breeds social fear and it is an eradication of what it means to truly accept a country - to acknowledge its faults as well as what makes it great in the eyes of many. While I know students have the option to reject saying the pledge, the implied social ostracisation from rejecting this forced nationalist action is something I find equally abhorrent as everything else I have mentioned.
It's all just so wrong.