The only part of US society with any experience at all going into this in 2003 was the military, due to KFOR/Kosovo, and even that was exceedingly limited. Arguably, if the US had more experience in 2003, it might have been less willing to go into Iraq at all.
There were people who were just 100% anti-war in general, or anti Bush, or whatever, but because they were always screaming the same thing, they could be easily ignored -- kind of like calling every single death in a war murder, it degrades the term murder and makes actual murder much cheaper as a result.
Michael Yon (www.michaelyon-online.com) was probably the first to say things were actually going badly from 2003-2005, and then to document the surge and "awakening" which won Iraq.