Going into Iraq in 2001 was an abrupt and very serious mistake. The mistake lies more in the fact that the majority of Americans, especially our leaders, were very ignorant about Iraqi society and culture, which lead the extreme clashes and violence. One can't storm into a country and take over everything without experiencing retaliation, of course. It is more drastic however, because it is a Muslim society, and they view their invaders as those who are on a crusade and are trying to inflict their (Christian) beliefs onto them.
Presidential candidate Mitt Romney has his own view on religion and ties it into the death toll in Iraq. He believes that we are too often only commenting on the American death toll and don't pay as much attention to total Iraqi casualties. He believes that we are all one family and should look out for each other accordingly. Unfortunately, that's not how society really is and probably never will be.