Believe it or not, this is a really hard topic to find books or resources on. I had to do it for work -- we did a Veterans Day program for kids. I wanted to do stories and crafts. It was hard to find something that didn't glorify war (society in general does enough of that) and lent itself to being read out loud. Because of bureacracy, I couldn't get a library card for the town my job is in without going through the library director. So one of the board members went for me.
My favorite was This Land Is Your Land. I think Woody Guthrie is credited as the author. You all know what that one's about, but the illustrations in it were really beautiful. You could have framed each of them. There are also some verses at the end of that song that generally don't get sung, questioning how free the country really is, and whether this land really is made for you and me. I'd never heard them before and it made me smile at how that song's always turned into a rah-rah patriotic song. It's like when Ronald Reagan used "Born In the USA" as his campaign theme song. I guess he didn't listen to the verses!
Another good one was called The Star-Spangled Banner. It was more factual and explained all the symbols of the country: the different places, people and objects that just scream "America". Finally, Yankee Doodle told the story of that song. I wish I had the books with me so I could say who wrote them. But I can't remember -- shame, as I'm posting this partly for anyone else who anticipates finding themselves in the same boat next year. If the board member hasn't picked up her books by later in the week, I can post them.