>>25554273Superman was given honorary citizenship to all the countries in the world by the UN back in the 60's, The "renouncement" was in a short story (may not even be in continuity) that had Superman doing it as a response to prevent his actions from being seen as US policy and causing political strife since he primarily works in the US and is seen as a US hero.
Ultimately this gets Superman back to the core original design of the character. When he was first introduced in the 1940's radio show they stated he fought a neverending battle for Truth and Justice.
The "American Way" part was only added during WWII and removed again soon after, only resurfacing as part of the 1950's TV show with George Reeves during the Red Scare.
It was popularized during that time, and there's certain RL political elements that seem to dislike any challenge to anything established in that era, even if originally Superman had no apparent national basis.