Shiites and Sunnis
note: Afghanistan lies directly east of Iran and is 80 to 85 percent Shia.
This handy map (click to enlarge) showing Shia and Sunni populations of Middle Eastern countries ran with a McClatchy story about Syria that categorizes the Syrian uprising as a sectarian (Shia vs Sunni) struggle. The lighter the shading, the more Sunnis love there. The darker the shading, the more Shiites live there. I don't know why they chose darkness culminating in black for the Shiite countries unless it's because Iran is mainly Shiite and they are participating in the process of demonizing Iran, which is a process our government with a lot of loyal help from the media goes through before they bomb a country.
While sectarian considerations may be a determining factor in relations between countries, it is usually a mistake to simplify an internal situation as sectarian, i.e., as a conflict between Shiites and Sunnis. Things like class divisions, tribal divisions and regional divisions are usually more important considerations when it comes to internal politics.
Few Western reporters have more than a cursory knowledge of Middle Eastern history and Middle Eastern countries, and most don't even speak Arabic, so they often resort to the "sectarian divide" analysis to explain things and to try to understand them themselves.
Syria, like other countries that were drawn up by colonial powers or that emerged after the European colonial era, is ruled by the sect that is in the minority, the Shia. Syria is allies with Iran, which is predominately Shia. But internally in Syria, the support President Bashar Al Assad has comes from the business people and the large numbers of the new Middle Class who have prospered under his rule, including large proportions of the two major cities, Damascus and Allipi, which have remained relatively peaceful during the now year long uprising.
In Iraq, where there is a lot of sectarian violence, there was no sectarian divide until the United States came in and made one. The George W Bush Administration's plan for Iraq even before 9/11 was to divide that nation into its religious and ethnic components, the easier to steal its oil. Before the Bush Administration implemented the divide and conquer techniques used by Britain throughout its former colonial empire, Iraq's Shia, Sunni and Kurds lived alongside each other and intermarried, and religious differences were overlooked, much as they are in a country like the US, where the friends we keep, the guests we invite to dinner and even who we marry are not selected according to what religions people are but according to such things as whether we work with them, share interests with them, went to school with them and etc.