I think I see the prism they see the world through.
Not too keen on the word unAmerican as I have no idea what being American is meant to be. That's to say there are many different Americas. There are types of American I like plenty. And there are types that I dislike too.
The ones I tend to dislike think they are exceptional, behave selfishly, overtax the flag, talk too much about rights and too little about duties, claim to be victims of everyone else, and so on.
The ones I tend to like share a common humanity, discover, invent, start small businesses, are kind and thoughtful, have a muscular character, and so on.
There are so many people and so many types. I don't know how anyone is meant to know what an American is meant to be.