Another weakly-linked trading alliance in which the individual countries retain their independence and largely go there seperate ways except in closely-defined areas. The core of the MC is an alliance between Spain and Italy post ww2 on the basis that nobody else would talk to them (which gave rise to the joke "Mussolini talks only to Franco and Franco talks only to God."). As the threat of the Caliphate grew, the Mediterranean Confederation was joined by Greece, Turkey and the Balkan states (initially Yogoslavia but then the successor-states to Yugoslavia when that entity broke up).
The Mediterranean Confederation has its tone largely set by Italy that underwent a renaissance in the 1950s and 1960s and became the world leader and trend-setter in style, fashion etc. People buy luxury Italian sports cars, women salivate over Italian fashion shows, Italian trends in art, literature, architecture are all watched and copied. The country gets compared favorably with the U.S. that is seen as a cold, technology-obsessed soulless entity by comparison. The rest of the MC basks in the light reflected from Italy. Anybody who has any pretensions to being anybody goes to Italy in holiday (and the really rich have a summer home in Tuscany).
There is no common domestic factor linking the members of the MC. They all differ drastically and the looseness of the Confederation allows that (was designed to allow that) to continue. Italy is Catholic and hedonistic, Spain is Catholic and bleakly moralistic, Turkey is Moslem with a secular government, some of the Balkan states are military dictatorships.