The fact is Tamilians were cleverly and virtually divided as Bs and NBs by straight forward rationalists (?), which paved the way for smooth sailing of others, especially Andhraites and Keralities. Still Tamilians, both Bs and NBs, have not learned lessons.
As Iyers and Iyengars have two different distinct systems, unity becomes a distant dream, which is not possible.
I have a feeling that Tamilians cannot be united, whether in India or outside, unless a Tamil Social Reformer with compassion, like Vallalar, who has faith in religion as well as the welfare of Tamilians, can only bring unity among Tamilians. Alternatively, the liberal minded Bs and NBs join together and educate the people the need of unity.
But, I doubt very much that this will happen.