"You are talking about foreign policy as if it has no domestic effects apart from those perpetrated by terrorists. That isn't true. The burden of occupying and governing vast territories that are not part of the nation taxes republican government beyond its administrative ability and causes it to collapse. We need to understand that now and choose wisely. "

[love to talk about that roman thing, but fear I shall be distracted, suffice to say USA is quite different than Roman Empire- though I think as analogy it is valid & can be useful.]

First of all as far as land area, Afghanistan is about twice the size as Iraq. If there is any quagmire on this planet, it's Afghanistan- it fits the profile best. I see no reason to think we can't use a similar model in Iraq as we are applying in Afghanistan. No one imagines we will have a short commitment with Afghanistan & it has all kinds of problems associated with it. The only reason we attacked Afghanistan was because it's leadership was too stupid to know what a mistake they were making by not dealing with the murders who attacked us.
Iraq lost their war. They thought they would be "allowed" to take over Kuwait. They were wrong. They signed a surrender agreement. Then they thought they didn't have to honor it. If it was an unreasonable agreement like Germany signed after WWI, then they might have gotten away with it. But their is nothing unreasonable about not having weapons of mass destruction. And Iraq wouldn't get away with it.
The problem is Saddem is stupid- this is normal, he is a psychopathic criminal. Psychopathic criminals are delusional; they are not rational. He controls people by threating to kill & torture them. We aren't afraid of this sick dog, and if we have to, we will kill it.
The only reason we didn't do this eariler, was because of the reasons you have given above. It was simply not worth the expense in money and US soldiers lives. But we haven't gone soft, we have the strongest miltary in the world, and we will use it, just like we were willing to fight in the WWII- having one weakest poorest trained army in comparison to other world powers at that time, at the time we decided to get involved with the endless European conflicts [for the second time]. By the end of WWII we had the strongest, best trained army on the planet- USSR had the next strongest army, and we had helped them with bringing this about.
There is no question that we can destroy Iraq's army, and without a army, Saddem & and family are dead meat. Btw, in the war with Iraq we had less casualities then compared to the same length of time of peacetime- first time war was safer than not going to war.
Any war of course is dangerous & over confidence can be problem- you need the leadership that allows for all the possible risks.
After the war is won, we will have problems- different parts of the country will want to have a independent state. What are we going to do about this? This is an especially difficult problem, because of our close NATO Member, Turkey. The Kurds live in both Iraq and Turkey.
And we also have the problem with oil assets. As general rule, we should not allow the splintering of the Iraq state, but we should be looking at compromises. Different ethic groups shouldn't be a reason to have a separate state, though undoubtively there will be a high degree of hatred from all of the oppression. If probably will need to get some sort of peace agreement and way of resolving grievances between injuried parties.
Anyways, there is no doubt this will be hard and will require good leadership from people who have been tormented for decades.