Could the US military have stopped the Benghazi attack?

No, and the bipartisan Senate Intelligence review is quite clear on this. One of its 12 core findings is that “there were no US military resources in position to intervene in short order in Benghazi to help defend the Temporary Mission Facility and its Annex.” Other congressional reports have come to similar conclusions.

Besides the seven person Tripoli-based team that assisted in the defense and evacuation, the only nearby available assets were unarmed surveillance drones. The closest armed aircraft were in Djibouti, at a base as far from Benghazi as DC is from Los Angeles, as Major General Darryl Roberson put it to Congress on November 2012. There were four Green Berets assisting in a separate evacuation mission in Tripoli, but the plane available to fly them couldn’t have arrived at Benghazi until 7:00 am — after the attack ended.