not only a war launched under false premises -
but in the planning was based on wishful thinking -
(in war you hope for the best but plan for the worst -
here the Administration only planned for the best and
didnt even consider the worst. IN fact anyone who entertained
other ideas - was dismissed or cast aside.

and managed with total incompetence.
(allowed the looting of the museum, the ministry of defense (that had all the fedayeen records- youd think you want the names and addresses of the people attacking you)

and marred with corruption (billions of Iraqi reconstruction dollars

missing or spent on non-existent projects etc)

for Bush (and Blair) to actually admit a mistake is quite difficult - not just that so many people have been killed, but that the ultimate outcome was counter productive. The Iraq war recruited thousands for AlQaeda, rather than eliminating WMDS it emboldened North Korea and Iran to go ahead with their nuclear weapons programs - without fear of much US retribution (since they are mired in IRaq - and easy targets there)
It also is a financial burden on the US economy (some economists such as Joseph Stiglitz estimate the long term cost between $1& 2trillion)

It alienated much of the US's European allies, and lost much of its moral authority After Abu Ghraib and Guantanamo.

The US went into this with the most powerful military in the world,
and yet it is unable to maintain security in a small country -
that is also a powerful lesson.