Nationalism is important for the survival of people, religious nationalism should be an integral part of every nation's nationalism, but race & culture are equally important. The collapse of the Ottoman Caliphate can not be blamed solely on racial nationalism, but on the corruption prevalent in the Ottoman empire. I could provide you with documentaries on the Ottoman empire if you wish to learn about its collapse.
Religion's main purpose is to guide you to the straight path so that you may be successful in the after life.
I didn't fail to understand that, if you read my post; I clearly stated that religious unity should be given as much importance as racial, cultural, & linguistic nationalism. There are many reasons that racial unity is important, one of them is the survival of the race itself.
You pray side by side to worship God as a community, it will not necessarily unite entirely different races. It is a ritual & while it does aid in creating a communal bond, it isn't the most effective method of doing so & loads of other methods are used to develop a feeling of unity. Studies on culture, the history of different nations, & cultural exhibitions are other good methods of creating unity.
Religion is exactly as it was, some people may not understand it, there is no doubt about that. Many people have lost interest in religion, but that's a subject for another discussion. Sorry, I am in a hurry, & that's why I couldn't give you an extremely detailed response.