Jimmy is the intelligence officer for the AFO teams in Medal of Honor. He uses satellite imagery to guide Neptune and Wolfpack through their missions. Also it seems that he has worked with AFO teams before, suggesting that he might be a permanent member of the AFO unit. This is shown in the cutscene where he tells Drucker that AFO Wolfpack is riding in to position and points out, that Wolfpack likes to move fast. He seems to possess great knowledge of the AFO teams.
He might be a civilian contractor working for the government, since he doesn't wear a military uniform, then again AFO consists of SOF members and they wear civilian clothes.
US Army Major Jimmy was also the name of Pete Blaber's deputy at Bagram during Operation Anaconda, which could mean that Jimmy was actually apart of AFO and was a serviceman.