It is hard to determine why Iraq receives so little U.S. attention as it drifts towards sectarian conflict, civil war, and alignment with Iran. Tensions in Iraq have been rising for well over a year, and the UN warned on June 1, 2013 that "1,045 Iraqis were killed and another 2,397 were wounded in acts of terrorism and acts of violence in May. The number of civilians killed was 963 (including 181 civilian police), and the number of civilians injured was 2,191 (including 359 civilian police). A further 82 members of the Iraqi Security Forces were killed and 206 were injured."
This neglect may be a matter of war fatigue; the result of a conflict the United States "won" at a tactical level but seems to have lost at a strategic level. It may be the result of the fact the civil war in Syria is more intensive, produces more human suffering, and is more open to the media. The end result, however, is that that the United States is just beginning to see how much of a strategic pivot Iraq has become.
The strategic map of the region is changing and Iraq's role in that change is critical. It used to be possible to largely separate the Gulf and the Levant. One set of tensions focused on the Arab-Israel conflict versus tensions focused on the Gulf. Iraq stood between them. It sometimes became a crisis on its own but always acted as a strategic buffer between two major subregions in the Middle East.
However, it has become clear over the last year that the upheavals in the Islamic and Arab world have become a clash within a civilization rather than a clash between civilizations. The Sunni vs. Alewite civil war in Syria is increasingly interacting with the Sunni versus Shi'ite tensions in the Gulf that are edging Iraq back towards civil war. They also interact with the Sunni-Shi'ite, Maronite, and other confessional struggles in Lebanon.
The "Kurdish problem" now spreads from Syria to Iraq to Turkey to Iran. The question of Arab identity versus Sunni or Shi'ite sectarian identity divides Iraq from the Arab Gulf states and pushes it towards Iran. Instead of terrorism we have counterinsurgency, instability, and religious and ethnic conflict.
For all the current attention to Syria, Iraq is the larger and more important state. Iraq is a nation of 31.9 million and Syria is a nation of 22.5 million. Iraq has the larger economy: Iraq has a GDP of $155.4 billion, and Syria had a GDP of $107.6 billion in 2011, the last year for which there are useful data. Most important, Iraq is a critical petroleum state and Syria is a cypher. Iraq has some 143 billion barrels worth of oil reserves (9 percent of world reserves) and Syria has 2.5 billion (0.2 percent). Iraq has 126.7 has trillion cubic meters of gas, and Syria has 10.1. Iraq has a major impact on the overall security of the Gulf, and some 20 percent of the world oil and LNG exports go through the Gulf.