In a piece in the New York Review of Books, Hiltermann contended that despite talk of Iranian meddling, Tehran has failed to accomplish a principal policy goal in Iraq -- securing a unified political coalition that could ensure Shia dominance in Iraqi politics.

Hiltermann lists a number of instances in which foreign powers have tried and failed to exert influence over Iraq.

In 2008, for example, Iran failed to prevent the U.S.-Iraq security agreements from being signed, despite its many summonses of Iraqi leaders to Tehran, he noted in an article entitled "Iraq: The Impasse."

In December 2009, Iranian soldiers occupied a well in an Iraqi oil field near Iran's border, raising the Iranian flag and claiming the well was their territory, he noted.

That outraged Iraqi politicians, as well as leaders of the Islamic Supreme Council of Iraq, which is often accused of being an Iranian proxy, he wrote.

But some experts argued that Washington will continue to play a major role in Iraq, as U.S. policymakers are concerned about preserving their investment, in terms of lives lost and financial and military costs.

"That's why we are seeing such a large U.S. training component being left behind and an enormous diplomatic presence in Baghdad," said Torricke-Barton.

The fact that U.S. combat troops are pulling out does not mean Washington will be unwilling to intervene in the future, such as with the use of drone strikes, air support and aerial reconnaissance, he said.

But many fret that Iraqi forces are not up to the job of providing full security once the remaining 50,000 U.S. troops pull out in 2011.

Moreover, the deadlocked political process poses a problem for the United States, as its goal of troop withdrawal can not be met without an Iraqi government, according to Stratfor.

With 50,000 U.S. troops still in Iraq, the United States does not yet face a crisis, but that could change if it continues its withdrawal to the point where the Shia feel free to launch sustained and escalating attacks on Sunnis, Stratfor wrote.

At that point, an Iraqi government must be in place, be united and command sufficient forces to control the country if it wishes to avoid such an occurrence, Stratfor wrote.