"On The Other Claw...."

I don't think they have coopted any concept. Nationalism, the modern nationalism, was essentially defined by Napoleon, Bismarck and Hitler. Patriotism has always been used to justify terrible violence, both foreign and domestic, rationalized as being necessary to "the state". I think the cooption is in trying to change patriotism from its roots as an emotional orgy of destruction into something it was never meant to be and, perhaps, cannot be. A rational patriotism would not favor one's own state, believe in their own special national destiny or any kind of exceptionalism, it would expand into a general humanism, a benevolence towards everyone now alive and those yet unborn, IMO.

As you pointed out, in 1940, the US was not strongly anti-Nazi. Indeed, large elements of our society were pro-Nazi. As the post you linked to said, Americans mythologize our past in order to avoid talking about unpleasant things - like how and who was pro-Nazi. The great legacy of the US is not really punching Nazis in the face. That's a fantasy, man, and always has been.