It is not like Muslims are disunited. Rather, Islam spanned across multiple continents which has different independent cultures of its own. Again same thing with Christianity and Buddhism too...Nations, people, and their emotions get united based on culture more than religion. For example, Philipines may be a Christian country, do you ever see the whole West stand behind Philipines if there will be any problem? Rather than the Philipines, people from China, Vietnam, and other East Asian countries will be feeling close to them.
You can extend the same mindset to Arabs and Turks too...Arab and Turkic people have their own civilizations and distinct culture. Even if they are Muslim, i believe, they feel closer to their co-culture people than any South Asian Muslims...
Now, last but the least, in my personal experience, I fear you may not like it, my Lahori friend come to my home and drop off and pick up my son when i go to India than any Hindu from Fiji who is same community....So we may like it or not, Pakistani people may politically hate us, but at human interactions, they are closer to me or even Hindus more than other cultures.
Well, you reap what you sow.