Civilian casualties would be high, which is probably why the US has reportedly talked them out of it.  I wonder who will talk the US out of bombing Iran, once the decision has been made.  It’s obvious from our fallen drone that the CIA is already busy within Iran itself, in some capacity.  Even our blunders and spying themselves may lead to another war, especially when those in charge are so war-happy.  From the Atlantic:

Fallen U.S. Drone Nearly Led to Covert Strike in Iran

New reports on the CIA drone lost in Iran last week reveal the scope of the stealth plane’s mission and just how far the U.S. was willing to go to recover it. The Associated Press reports on Wednesday that despite U.S. military statements Monday suggesting the drone was lost while flying a mission in western Afghanistan, Iranian officials say the RQ-170 drone was detected about 140 miles from the border of Afghanistan, deep inside the country’s air space. U.S. officials, speaking on background, confirmed the RQ-170 drone had been spying on Iran for years but did not indicate the extent to which it penetrated Iranian air space. They did say the U.S. air base in Shindad, Afghanistan, was designed to launch “surveillance missions and even special operations missions into Iran if deemed necessary.”