With him renouncing, I think the intention there is to step away from the PERCEPTION that he's American. Because he's completely viewed as a Western hero, isn't he? And that's not going to change any time soon, but if he states it, it's always going to be symbolic, isn't it? Clark Kent is a US citizen, but Superman is above such distinctions.

There was an issue of Joe Kelly's JLA run that dealt with a similar point with regards to the Justice League having "of America" in their name. How their DOES need to be that separation.