Dear Youdont,
I am getting the sense that you want to only discuss the halachic permissibility of an eiruv in Brooklyn versus other American Cities. Now, this issue is not in a vacuum. The real world influence has been alluded to numerous times. I don’t know how you feel about it.
The Halachos of Eiruvin have three distinct fields of application.
1. The townspeople are supposed to build an eiruv.
2. The specifications to which the eiruv can be built.
3. Carrying in the eiruv.
The permissibility of an eiruv is the second field. Comparing cities is the first field. So, we keep missing each other’s points.
I apologize for the animosity. Let me clear up some of our misunderstandings and then I’ll clarify what I can about Rav Moshe’s position.