What is the goal in Iran based on recent history?

Let's review a little history.  In 2003, then President Bush sent the US military into Iraq because Saddam Hussein (who the US supported with his war with Iran) had "weapons of mass destruction (WMDs)" that posed a clear and present danger to the US.  Saddam Hussein supposedly also supported Al Qaeda (unsubstantiated) and was going to use those WMDs agains the US (even though after almost 12 years of economic sanctions and no-fly zones, Saddam was in no position to do anything but try to rebuild his infrastructure).  By taking out Saddam, the US would be safer and democracy would be restored in Iraq.  Now 12 years later we are still flying missions and have quietly increasing the number of ground troops and Iraq is pretty much in chaos (and Mr. Obama and his administration have done nothing but continued this atrocity).

After 9/11, we had to do something so former President Bush invaded Afghanistan in 2002 supposedly to hunt down Al Qaeda/Osama bin Laden (even though when the CIA worked with UBL during the 1980s, he was always in Pakistan.  Imagine the surprise when we "found" Osama bin Laden in Pakistan during the 2011 raid!).  US troops were supposed to eliminate the Taliban (who were not the same Al Qaeda supposedly responsible for 9/11 but were close enough for government work).  By inference, by eliminating the Taliban democracy would replace Islamic tyranny.  Under that guise, 16 airplanes bought for Afghanistan to the tune of $500 million which we then summarily sold for scrap (around $32 thousand) when the US pulled out.  Now Mr. Obama has quietly agreed to slow the withdrawal of the remaining 10,000 US troops AND has requested $3.8 billion to fund as many as 352,000 Afghan forces through 2017 (DW).

Obama and Clinton wanted Qaddafi out of the way, again inferring that democracy would replace tyranny in Libya.  Instead anarchy has flourished.  Likewise, they hoped the same thing would happen once Asad fell that would allow them to position the next domino to fall, Iran.  But when that didn't happen, Obama and now Kerry playing the part of Hillary had to fall to plan B.

Plan B seems to be negotiating a nuclear arms agreement with Iran (who is supposed to pose some long range threat to the US).  The grandiose initiative though keeps getting overshadowed by the ISIS/ISIL/IS/Daesh mass executions and now threats against US troops at home.  (Working a deal with Iran is actually nothing new for the US, however, if one remembers a nasty little episode called the Iran-Contra Affair.  Basically sell arms to Iran to get several US hostages released and in-turn use the money to fund the Contras in Nicaragua.)

Giving these attempts to send in troops to eliminate tyranny/terrorism and install democracy, one wonders what the real goal is with Iran?  The US has been wanting regime change there for at least 35 years and so far, things are now different then when the Shah was chased out of Tehran.  Syria shows no signs of losing Asad and at this point, it would allow Daesh to seize control of Damascus.

To all of this, here is the real question.  Unless O'Malley manages a Jimmy Carter or if Ted Cruz usurps Jeb Bush, we are most likely to see Clinton and Bush running in 2016.  If that happens, what are the chances that any of things going on now will change for the better?