Members of the local Syrian community rally against the United States' involvement in Syria, in Allentown, Pa., Aug. 27, 2013. (Chris Post/AP)

Stuart Bowen, the special inspector general for Iraq reconstruction since 2004, hasn't been consulted by administration officials considering military action, but on Thursday he shared his opinion on what Americans can expect in a post-Assad Syria.

"Should [Syrian President Bashar] Assad fall, the needs are going to be immediate and substantial," Bowen told reporters at an on-the-record breakfast meeting. "Like it or not, we're going to have to play a significant role."

Drawing from his decade of experience in neighboring Iraq, Bowen advised a multilateral, yet well integrated, approach to rebuilding Syria, where an estimated 100,000 people have died in a two-year civil war.

"What we like is to help a state that's slipped into failure get back on its feet" and then leave, he said.

That's not what happened in Iraq, where reconstruction expenses alone cost American taxpayers at least $53 billion over nine years, or $15 million a day. "Taxpayers are rightly exhausted" by those efforts, he said.

One of the biggest lessons from Iraq, outlined by Bowen in a March report, is that there should be a unified command structure administering aid, to ensure accountability and shared goals.

Iraq reconstruction, he said, "tapped out our treasury" and "successes have largely been the exception" due to poor planning and coordination.

Bowen's team of investigators recovered nearly $200 million in fraudulently spent U.S. aid, but the chief inspector believes the actual figure could be three times greater. His team's final report says $1.61 billion in U.S. tax dollars could have been saved with better administration.

If the U.S. delves into Syria, Bowen recommends administering aid from different sources and countries in a manner similar to the Federal Emergency Management Agency, which responds to domestic disasters within the U.S. FEMA, he said, has a unified command structure with standing relationships with contractors, who he said "should have a place at the table when we're planning" a reconstruction effort.

Security must be ensured before pouring money into large-scale projects, he said.

"It's too late to learn these lessons in Afghanistan because we are on a departure path," he said. "It might be Syria" where the lessons could be useful.

Other lessons for a possible intervention in Syria offered by Bowen include restoring national sovereignty as soon as possible and quickly stabilizing the country's financial system.

Former Syrian economics minister Abdullah al-Dardari, who is leading a six-member U.N. team assessing reconstruction, estimated in May his country likely needs at least $28 billion to rebuild homes and basic infrastructure alone.

The U.S. Marshall Plan successfully helped European countries rebuild after World War II, Bowen said, because it was centralized, depended in part on loans and was well-planned in advance.

It's frustrating, he said, to "see so much ground being lost in Iraq" since U.S. troops left in 2011, particularly recently.

But, Bowen said, Iraq – unlike Israel – isn't likely to be targeted by the Assad regime as revenge for a possible western military attack. "Iraq is aligned with the Assad regime," he said. "Iraq is aligned with Iran and Iran is aligned with Syria."