"Seymour Hersh wrote in The New Yorker that undercover American troops were already in Iran collecting precise targeting data needed by US weapons systems and to establish contact with ethnic groups antagonistic to the Iranian regime."
To make matters worse, the nuclear option may still be on the table, as there is no reliable way to destroy properly fortified underground bunkers using conventional weapons. Atomic weapons, with their incredible power can rip asunder even the most fortified bunker.
According to the CIA world factbook, Iran is the number 4 oil producer in the world with 3.98 million barrels a day of oil production (or almost 5% of total production). While none of this oil reaches the United States, it does go to Asia and Europe. A temporary disruption in production from say, a nuclear attack on Iran by the United States resulting in all the workers fleeing for shelter from the fallout, could create a MAJOR crisis on the worlds oil supplies.
Basic economics: if supply can't meet demand, prices will rise until demand drops. Without even half of the 3.9MM barrels from Iran for a period of a few weeks, the worlds oil markets will go into meltdown.
Interested in non-Opec oil supplies? Check out this link to the Department of Energy's Non-OPEC fact sheet.