Surely, Iran has emerged empowered in Iraq over the last eight years, and it has a sympathetic Shiite-dominated government to show for it, as well as close ties to the anti-American cleric Moktada al-Sadr. But for what so far are rather obscure reasons — perhaps the struggling Iranian economy and mistrust toward Iranians that has been nurtured for centuries — it has been unable to extend its reach.

In fact, a host of countries led by Turkey — but not including the United States — have made the biggest inroads, much to the chagrin of people here in Najaf like the governor.

“Before 2003, 90 percent of Najaf people liked Iranians,” said the governor, Adnan al-Zurufi, who has lived in Chicago and Michigan and holds American citizenship. “Now, 90 percent hate them. Iran likes to take, not give.”…

The patterns were established soon after the American invasion. Shoddy Iranian goods — particularly low-quality cheese, fruit and yogurt — flooded markets in the south, often at exorbitant prices, said Mahdi Najat Nei, a diplomat who heads the Trade Promotion Organization of Iran office in Baghdad. This sullied Iran’s reputation, even though prices have since plummeted, creating an aversion to Iranian goods that lasts to this day, Mr. Nei said.