If Egypt knew and did nothing, then Egypt is at fault. Even if they notified the U.S. and did nothing else. They are the host country and they are obligated to protect the American Embassy by the U.N. convention.
If the U.S. knew and didn’t take precautions then heads need to roll here and I’d say murder charges are in order.
Don't be silly. That serious of a charge is for the makers of the film.