About 100 countries in Europe, N.America & S. America having different versions of Christianity are doing well without being United. None of these countries have ramadans, umras and haj or gatherings.
They are not enemies of each other, do not attack each other, neither kill civilians of each other.
They had wars in past yes, but not anymore, they learned.
When Muslim are going to learn or will they ever, it's over 1400 years.