The WHOLE social infrastructure was under Hussein's control. It had to be dismantled and built up from scratch by allowing BOTH the Sunnis and Shiites to be participants in its workings. How can you go to another country, topple their dictator and yet keep the very elements that kept that dictatorship alive for the past 30 years? You can't. You have to get rid of those elements. It needed to be done.
In some cases, the USA allowed members of Hussein's personal guard to be part of Iraq's military and they paid for it because some of them were involved in organizing those "death squads" that went around killing Shiites.
The destruction of oil pipelines were done by Syrians, Iranians, Jordanians, and Saudis crossing the border trying to disturb the economy and the efforts to install a new government. Both religious factions were in a civil war for many months which contributed greatly to the Iraqi death toll. The USA made some mistakes. No doubt about it. But, the USA military is in no way responsible for the 10s of thousands of civilians that have died. You want to seek blame for that then just look at the friction between Sunnis and Shiites and the Jihadists crossing the border into Iraq.
