Regime change has been an epic fail. Look at Libya and Iraq. Libya is in the middle of a 3 way civil war.
Iraq is in a mess and even when ISIS is defeated there is still major issues. In Syria the rebels had and still have unlimited support but they fight each other more than they fight Assad. Thing I find funny is how the US government complains about Iranian influence in Iraq but forget that they overthrew Saddam and put a Shia majority government in Iraq.
Iran is Shia and so is 60-65% of Iraq. Of course they would have influence! Are they that stupid! Now there is talk of trying to stop this influence but it's too little too late. If anything ISIS rampaging Iraq was a boon for Iran and their proxies.
America really as no idea what they are doing in the region. It's easy to overthrow a government but it is hard to govern. America foreign policy should just give on regime change because there has been no successful case of regime change in the mideast.