Unfortunately geopolitics, like nature, abhores a vacuum.
Some power will dominate world affairs.
If it is not America, it will be someone else. Someone who may be hostile to American interests. China springs to mind. And there are worse possibilities than that.
In the old days Britain filled this role. They were the real reason the Monroe Doctrine was largely upheld through the 19th century.
But Britain's day vanished in World War II.
We would lose far more than you think by the kind of retrenchment you seem to have in mind.
In the meantime, I am still curious what kind of theories you might be entertaining about what Bush and his people really were motivated by in staging this war. It's speculation, I know. But I am curious. Indulge me.
Again, I have no first-hand knowledge. I have heard numerous speculations:
1) Washington wants to control the price of world oil (both to give DC better ability to modulate the US economy, and as a threat to other oil-producing nations to cooperate with us or face a price collapse).
2) Iraq switched its oil accounts from dollars to euros a year or so ago. This was a blow to the status of the dollar as the world reserve currency which, if emulated by other OPEC nations, would have severe negative economic consequences for the US economy.
3) It was an attempt at radical Reconstruction of the Middle East, similar to the South after the Civil War. One theory states that terrorism is endemic to the Middle East, and the only ultimate way to end it is to essentially invade and conquer the entire region, and then give them mass doses of US pop culture to transform them into clones of American consumerist sheep.
4) It was an attempt to show the Arab world just what we are capable of. The US couldn't allow the 9/11 attacks to go unanswered...we had to kick Arab butt...and Saddam was the most convenient target around.
5) And last, but not least, there is the ever-present theory that the Likudniks in American precipitated the war to shape a more secure environment in the Middle East for Israel.
Take your pick. But as I said, the only thing that I am fairly certain of is that the stated reasons (WMD and links to Osama) were BS.