That's true. The AR-15's predecessor jammed so badly in Vietnam that it was likely a significant cause of losing that conflict.
The AK-47 is far, far less likely to jam than even the best AR-15's, which still has a reputation for jamming.
You can fight with AR-15's just as well as you can with AK-47's, which is precisely what the Taliban have been doing for the last decade against the USA, and for another decade against the Soviets in the 70's.
moral of the story: emulate the Taliban
Exactly, a common belief is that a semi-automatic is automatically inferior. In actuality, Soldiers are trained to shoot their M16/M4s in semi-auto most of the time, because unless you are pretty close or extraordinarily talented, burst fire or full is just going to be a waste of ammunition. The reason machineguns (m249, m60, etc..) are usually shot in full auto, is because they are primarily designed as a supressive weapon system.