It's not just silly because Superman is a fictional character and therefore no more an American citizen than Popeye or Mickey Mouse. It's silly because it's a non-issue.
This kind of story has been done before (he's eighty years old; what hasn't?), where Superman is conflicted about entering into politically tense situations because he's seen as an American and as a de facto agent of the American government. It was a component of "Superman: Peace on Earth," as I recall, and it figured into some of the Bialya/Qurac stuff in the '80s, and into a plotline in Rucka's "Adventures of Superman" a few years back. The point that Superman is a citizen of the world, belonging to the world, a hero to the world, has been made many, many times. Renouncing his citizenship (heck, the guy's home is already in the Arctic Circle, and presumably not Alaska) is simply a way of freeing him from being hampered by his apparent ties to the American government and freeing the American government from having to account for Superman's actions. One would think that would be a welcome relief, considering how often the guy seems to go crazy/evil/megalomaniacal. Global politics and the American government should not be a limitation on the good that Superman can do, and they shouldn't want to be.
The other side of this is the idea that Superman is somehow leaving behind or repudiating "Truth, Justice, and the American Way," and I really don't get that impression. He says "'Truth, Justice, and the American Way'--it's not enough anymore," but that doesn't suggest that it's wrong--just limiting, or limited. I hardly imagine that Superman is going to stop fighting for truth and justice; heck, this story is about Superman seeking the liberty to dedicate his life to the pursuit of happiness for all people, equally. He's declaring his independence from American politics. Put another way:
When in the Course of [super]human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.I don't know; it sounds like the American Way to me.
I'm slowly working my way through Elliot S! Maggin's Superman: Last Son of Krypton, and one thing I like is how he presented the Ethics of Sonnabend, the basic principles that have somehow found their way to every civilized corner of the universe in one fashion or another.
Loosely translated into English, some of Sonnabend's ethical standards could be stated like this:In other words: Truth, Justice, and the American Way. The problem is not in the principles, but in how others interpret Superman as a tool of American political power or imperialist intent. And with at least one writer on the Superman books (the inestimable Chris Roberson) explicitly influenced by Maggin and the novels, I suspect that this point won't go unnoticed.
Do not bear false witness against your neighbor.
Do unto others as you would have them do unto you.
We are endowed by our Creator with certain inalienable rights including life, liberty, and the pursuit of happiness.
The final point is this: Superman is a citizen of the world, and frankly, that's how it should be. But I guarantee you that Clark Kent is still registered as a citizen of Metropolis, USA. Not only would it be pretty damn obvious for Clark Kent to renounce his citizenship at the same time as Superman, but there's no reason for it. Superman will still be the hero of Metropolis, Clark Kent will still report for the Daily Planet, and the status quo will remain basically in place as it has for decades. Not even Superman could budge that.
When you can hover above the world, you don't see political boundaries.
And that's the way it should be.