Had he won in 2000, Gore might have been President, so I kind of see his point about the Iraq War may not have happened.
I would imagine that a President McCain would have nuked half of western Asia about three days after 9-11. Thus he’s right, there would have been nothing to invade in Iraq.
Somehow, one suspects, towards 2003 the U.S. under McCain would have started an even bigger war with China and/or Russia. Most of us would probably be reading this in heaven although some maybe somewhere else.