Cognitive dissonance is a mainstay of politics, conservative politics in particular. Exercising control of a populous means that you will do damage. To believe that you are doing a greater good by exercising harm requires the kind of buy-in that allows you to rock out to the chorus while ignoring the verse. This is not about being smart or being dumb. It is about empathy.
dumb? or willfully ignorant? I know Occam's razor applies here, but Sometimes, when it comes to music, people hear what they want to hear and miss the actual message.
Frankly, does it matter what the lyrics are? Half of the lyrics are unintelligible, and the other half is somewhat ambiguous, and you really have to pay attention to get the actual meaning of the song. To anyone but someone who's sitting at home actually listening to the lyrics, the song seems like an obvious fist-pumping american anthem, and if Springsteen didn't want people to think that, he could've tried not making it sound so anthemic. If politicians use it, I don't think it has much to do with their allegedly low intelligence. It's probably rather that they don't care about the actual message of the song, they care about what the song CONVEYS. And to 90% of people, it conveys "AMERICA, FUCK YEAH!"
I think he's being sarcastic, but I think the real reason most people don't get it is that he slurs like a drunk, in addition to his somewhat oblique lyrics.