There has been an increasing trend among many young Muslims who are upto the task of erecting a Caliphate, and if not Caliphate, then pushing for an Islamic brotherhood to recognize the status of Muslim Ummah.

But realistically it is not possible at all. I am not a nationalist at all, and dislike it, but its opposite ideology, globalism or internationalism is not possible either. Its a huge mistake to believe that erecting a Muslim Ummah magically solves the nationalistic conflicts of the Islamic world.

Say for instance, during the first world war, the British empire lured the Arab Muslims to fight against Ottomans in exchange for Arab nationalism/independence. However, they did not honor it fully as they forcefully created a Jewish land among the Arab nations (very cunning of the British empire to get rid of its own antisemitism).

On the other hand, after the Great War, Muslims in India were revolting against British empire in support of Ottoman Caliphate. However, the Caliphate was abolished not by the British, but by the Turks themselves. The Indian Muslims made an absolute disgrace of themselves. After failing with this movement, Maulana Azad had to resort to his own nationalism. Whereas, a guy like Jinnah could care less about what happens in a different part of Muslim world, and came out to be correct.

So, there is no point in supporting the Muslim Ummah at all, since you do not know which part of the Muslim world reacts to which events. However, that does not mean one cannot condemn the atrocities, such as Israeli atrocities. But, a Muslim ummah does not solve this issue.