Maybe I'm not reading the text of the US pilots warning correctly but wasn't he warning that the aircraft could be subject to danger from another source if it continued? The wording used at the end of the Tx was 'you continue to fly at your own risk'. If the US aircraft had an aggressive motive it would have continued the intercept. If the airliner didn't respond when ordered to do so the US jet would have escalated its actions. This sounds like a routine warning about proceding; the Iraqi airline captain certainly doesn't seem to have felt the need for any precautionary action. Its amazing how the 'routine' can be twisted to appear more significant than it really was.
rgds
Shakey