Your challenge is to create a political confederation between some but not necessarily all countries that occupy areas formally belonging to the Roman Empire such as Italy, Spain, or the Ottoman Empire, and have this alliance become a supper power. Please focus on aligning countries that meet the requirements but that where not aligned in OTL.
I'd prefer a post 1860 POD but you may not limit yourselves to that. Also this may be possible with a post 1900 POD but if so I cannot think of how myself. Also I'd prefer a focus on aligning countries that boarder the Mediterranean.