Reddit mentions of Reset: Iran, Turkey, and America's Future

Well there's even more to the situation than this article mentions. The US was actually helping to arm both Iraq and Iran with the goal of helping to inflict casualties on both sides. A weak Iran and Iraq tipped the power scales in the middle east toward Israel and Saudi Arabia, which was and is the US's desired balance in the middle east powers.

To learn more about it, read Reset by Stephen Kinzer. It's a great book, as are Kinzer's other books.

I was also going to make a note but when I looked it up on amazon, it's apparently only $2.91 with free shipping (prime), so I just ordered it.

The present regime is heavily based off of a few core values:

1. Anti-Israel: Lots of Muslims/Arabs hate it, and acting as the prime lightning rod for anti-Zionism would theoretically get a lot of support from Arabs who would otherwise ignore their Persian ally. Many, if not most, Persians don't actually care about Israel and view it as an Arab issue; in fact, the Shah regime recognized the Israeli state and it isn't inconceivable that a post-Islamic Republic state would either. This may be outmoded however; Turkey had decent relations with Israel under Erdogan pre-Marmara and was never seen as an Israeli patsy. Still isn't, now that they're getting renormalized. Tangent aside, it's really just to play well with the Sunni crowd. Speaking of which...
   
   
2. Shiite supremacy: I'm a little sketchy on the religious aspects, but Iran has acted in a similar capacity to Shiite groups in Bahrain, Saudi Arabia, and others that other "missionary" (I made that up) states like the USSR and ex-colonial states do: they intervene in the affairs of other states by saying "your government doesn't represent your pro-Labor values/your ethnicity, we do!" Even if the US dropped its alliance with Saudi Arabia and Israel tomorrow for one with Iran, it would have to contend with its other Sunni allies that resent/fear Persian manipulation/support for the downtrodden.
   
   
3. Anti-Big Satan: Let's be perfectly blunt. Even if Iran could forswear any desire to help Hamas and other such groups win back their land militarily and stop annoying Saudi Arabia with its attempts to improve the lives of the Persians' co-religionists, there's the simple matter that the US supported the Shah and hasn't exactly been nice since the Shah. There's a bit of he-said, she-said/You sanction and let the Saudis/Lebanese/whoever suppress the Palestinians/Shiites, we attack (or other way around, I'm not sure and both sides will say the other started it by this point). There have been some attempts, including an Iranian offer to talk soon after the fall of Baghdad, but it all seems to be stuck at the moment. I just hope that things improve.
   
   Too Short, Need Meat: Check out Stephen Kinzer's book. It actually speaks to your question about America's relationship with Turkey and Iran vis a vis its relationship with Saudi Arabia and Israel. It's good.