The question is quite complex. Southwest Asia is a region that comprehends several countries that share some similarities but also very radical differences. In terms of religion, the majority of these countries are Islamic while the other ones are Christian and then there is the tiny state of Israel which is a Jewish majority. In terms of language, the three main languages are Persian, Turkish and Arabic and the remaining countries will speak Hebrew, Greek, Kurdish, Armenian, Georgian, etc. In terms of politics the region is deeply divided. Concerning the economy, both Turkey and Saudi Arabia have the largest economies and these are based on oil. Then there is Israel whose economy is very strong and diversified and Cyprus that politically, religiously and culturally is firmly attached to Europe. Since the majority of the region is Islamic, then religion could be said to be the MAIN unifying factor with the caveat that even this religion is divided between two major strains of Islam, the Sunni and Shia persuasions.
