"We support their retrograde dictatorship."

We have diplomat relations with enties which we acknowledge as soveriegn. Which is the opposite of imperial- if we didn't acknowledge independent nations then some other entity would have to represents that land area [govern it some fashion].
Or as the case with most of the surface of the Earth [international waters] no entity has claim- meaning no one who lives there has been recognized as having a right to claim territory- has rights to restrict other parties use of the area.

"We did the same with Iraq, until Saddam got too big for his boots."

Nonsense. Iraq was a state controlled by the Brits, which then became independent of the Brits and became a client state of Soviet Union. America supported Iraq in same degree that we are currently supporting Iran- meaning there is some effort to re-establish diplomatic ties. For example anyone representing America, in dialogue with Saddam's regime, was a special envoy- meaning we had no established diplomatic relations- no embassy building with staff in Iraq. At least in Iran there is currently an America embassy building- though it's currently used as public museum with an anti-american exhibt.

"We did the same with Iran, until the Shah became so autocratic that he paved the way for the Ayatollah."

You know speaking of empire, Persia was once a great EMPIRE and a lot Iranian are still basically living in a past of this great glory- the same goes for most of the middle east. I guess it would similar, if one day Americans woke up, and realized Latin America and/or Africa had starships and was trading aliens in distant star systems. Up until the 13th Century, Europe had little of value to the Middle east, other than raw material and slaves. And of course Africa was also a source raw material- mostly gold and slaves.
That Africa has long been the victim of imperialism is true, as long you understand it's mostly been Islamic imperialism.
As far as the Shah, there isn't much different from today's Egypt- other than Egypt has a history of being more involved in the modern world.

"We buy oil from client states. You have it right when you say we were a major exporter. We aren't anymore. So we seek to secure oil-producing areas so they will be more compliant."

It's not as though America couldn't produce enough oil for it's own consumption, but rather America laws restricts mining oil in America. But it's true that there is a lot oil in the Middle East that it's easy to extract and process.

Look if you have a large copper mine- meaning a large quantity of rich copper ore and cheap to extract the result will be [unless prevented in some way] that the mine will make a lot of copper. And if you have a dozen or so areas in the world where a lot of copper is made, then by distruption one of two of these areas it will affect the global supply of copper. A govt or private sector can counter this by stockpiling copper. It's wasteful [not efficent] to have huge stockpiles of anything- but no doubt it's profitable if supply is interrupted. A stable supply of anything is good for the supplier and good for the consumers. An unsteady supply of anything "provides a market opportunty" for agents that can store that commodity and sell when prices rise. IN OTHER WORDS unless you are in the oil business and specifically in the sector that has "stockpiles" in some form or another [it could still be in the ground, and the rate of pumping is increased] it doesn't benefit most people to have oil supplies interrupted.

"Notice how we tend to get involved in the affairs of nations who have something we want."

Or most people don't care about countries in far off lands, unless there is some circus entertainment involved with it. The few people who do have a real interest are involved in some way- which can include family connections being in that country- such as Ireland, such as Cuba, such as Lebanon, etc. And yes, of course it can involve business relations or even [the horror!!] relations having to do with some activity your church is involved with.

"Nations who don't have anything we want can go hang, until people like Nicholas Kristol holler enough to make us ashamed."

I don't know what Nicholas Kristol said that made you ashamed, but chances are it was bullshit- if that is any comfort to you.