We have had this "Ummah" discussion so many times here, but nevertheless I am going to give my views on it once again lol.
It's true that all Muslims are brothers & sisters to one another, & that they constitute one spiritual nation through religion. However this does not imply that we give up our race, culture, language, heritage, or nationalities simply for the sake of unity or living in a caliphate. God himself honors our diversity & wishes to preserve it, if He wasn't fond of it then why would He make humans so diverse & different? Islamic brotherhood aims to give people of a diverse background some sort of connection with each other so that they may not only help each other out, but also learn to appreciate & respect each other. Again, this does not imply destroying your race, culture, or language. Anyone who asks us to destroy our race, culture, language, or heritage is the embodiment of pure evil & must be utterly humiliated & destroyed.
Muslim nations are free to go on their own paths & help out other Muslim nations if they ever require it. That does not mean that you put someone else's interest above your own. If 2 Muslim nations have conflicting interests then they must do whatever is best for them & if that requires severing ties with another Muslim nation then so be it. A nation must never put someone else's interest before them. That being said however, Muslim nations should avoid conflicts or work to resolve pointless conflicts.
The problem with Pakistan is that the concept of Muslim "Ummah" over there involves giving up & destroying your heritage completely. Many in Pakistan don't know about or even celebrate their own history. In stead they take pride in the accomplishments of other Muslims who have nothing in common with them besides Islam. This is laughable of course because none of those Muslims are related to Pakistanis in either the genetic, linguistic, or ethnic sense. Some Pakistanis are so obsessed with "unity" that they might even bend over & sell their own daughters simply because a Muslim "brother" asked them to do so.
Nations require both racial & religious nationalism to survive, Arab nationalism is the best example of that. It aims to preserve race, language, & culture while simultaneously promoting Islam as well. Pakistan needs a mixture of both racial & religious nationalism so that their first priority would be to serve their own country & improve themselves while preserving their cultures & traditions. Then at the same time they could help out their Muslim brothers & sisters in other nations against injustice or any feasible or rational assistance they may require. Only when nations give first priority to themselves do they ever progress, no nation has ever progressed looking up to or relying on someone else.