Leader of the Caliphate? How is NATO being run? or other military Alliances like SCO? We don't need an out and out "leader" what your saying as non-muslim is just dividing us muslims by thinking that one Country, or set of individulas will lead/rule. The Ummah if ever had enough courage to resolve those very problems you high lighted such as, racism, tribal differences, sunni-shia divide and nationalism could become a dynamic force. If not atleast a powerful pressure group ensuring more protection of self interst than the current organisation of Islamic countries which is sometimes percieved as an elaborate tea party.I hate to tell you guys this but the Ummah re-uniting is not gonna happen, evne if everythign west ofJerusalem and North of Gibraltar suddenly dissapeared. The hard core islamo-facist like Al Queda or the Taliban, the Wahhabist, the Sunni-Shia divide, tribal differances, racial hatered, and national self interest all work against unity.
Just ask yourself this question...... Who is fit to lead the Caliphate.
Pakistan can't even unify, let alone the entire ummah. I think before you start dreaming of a world unified under Islam, you might want to get the tribes and chieftans of the NWFP to remember they are part of Pakistan.
Pakistan can solve PAkistan by itself, don't worry about it...