The problem was not with the initial invasion & occupation. We accomplished our goal years ago & are now bogged down in a quagmire of nation-building that has lasted longer than the Civil War, WWI & WWII combined.
It's long past time to get out (but a lot of people are getting rich off the continuing occupation).
We should never again spend Billions on schools, mosques, sewers, and roads for Muslim nations that hated us anyway.
But, remember this - the foolish generals always prepare to fight the last war.
The next one will not be like the last one - but it may prove to be like WW II or Korea, only bloodier.