I do think there is something as a Muslim Ummah. However, the relations between modern nation states are not affected by this notion. In the realm of international relations, interests reign supreme while romanticism takes a back seat.

I think that it is naive to think on the lines of Muslim majority nations supporting each other based on their shared beliefs unless the interests are also shared. Most importantly, it is worth remembering, that a state does what it perceives to be in its best interest in this temporal world not in a hereafter seeking validation from God. This is stating the obvious but it has to be said.

Here is an excerpt from a piece by Amir Rana on this topic:

“Foreign Minister Shah Mehmood Qureshi’s statement on the silence of the Muslim ‘ummah’ over India’s oppression of Kashmir reflects that Pakistan lacks some essential component to develop equal and robust bilateral relations with other nations. Fed with the narratives of the ummah and Muslim brotherhood since the country was founded, many in Pakistan wonder why the ummah only showed solidarity with their country when it was internally and strategically strong. It also vindicates the view that religion and ideologies do not provide any foundation for strong relations among nations. In reality, these remain secondary, and largely come into play when aligned with national interests of economic and strategic significance.”

Link: https://www.dawn.com/news/1501527/di...eign-relations