During Iraq / Afghanistan, Al Qaeda lost significant power in the terrorist-world. In its place, ISIS (Islamic State of Iraq / Syria) began to gain power. This destabilized Syria / Iraq / Jordan. USA put troops in Iraq / Jordan to help our allies (Kurds, Israel) and that's that.
Iran is also worried about the instability there, and they have their Shia-militia there.
There's a complicated set of politics between USA, Kurds, Iraq, Israel, Iran (and their militants), ISIS, and Syria (backed by Russia). Its a mess. The important thing is that Iran-backed militants attacked US troops in this region because of this whole Israeli flareup, but the region has been a mess for decades.
Islamic golden age and Ottoman rule was relatively stable actually. Sure there was a Crusade every century or so, but its not like the infighting we see today. From the Muslim perspective, it was the Crusader Kingdoms that were the source of that instability as well. But the Crusades were still relatively rare in the great scheme of Year 1 through Year 2000.
A big problem is that us Westerners (as a whole) don't realize how much these people crave the stability of the Ottomans. Literally centuries of peace, disrupted after WW1. And we ignore their culture and history, and wonder why they hate us... We have to remember the Muslim contributions to the world and the stability and peace that they once knew. Acknowledging that should go a long way towards peace IMO.
I'm not saying the Ottomans were necessarily a good kingdom or empire mind you. They were a middle-age Nobility that somehow survived into WW1 as a world power. But they did offer peace and stability to the regions they controlled, a peace and stability that has been ruined since the collapse of the Ottomans after WW1 treaties. The collapse arguably was going to happen anyway (Ottomans were definitely on their way out and is part of the reason why they lost WW1 so decisively). But I don't think this attitude of "they were always a mess" is historically correct, or useful in the scope of modern diplomatic discussions.
I agree with you, the Ottomans were a source of stability and were generally failing by WW1. I believe the drawing of the new borders while ignoring cultures and histories of the people left in the former Ottoman Empire is also a huge source of instability.