You want somebody to blame for all this, blame George Herbert Walker Bush. The causal trail leads right back to his doorstep.
Let's set the wayback machine: Under the pretext of helping Kuwait and the Saudis, Daddy Bush goes after the Iraqis.
During a speech to a special joint session of the U.S. Congress given on 11 September 1990, President Bush summed up the reasons for the incursion with the following remarks:
"Within three days, 120,000 Iraqi troops with 850 tanks had poured into Kuwait and moved south to threaten Saudi Arabia. It was then that I decided to act to check that aggression."
The Pentagon stated that satellite photos showed a buildup of Iraqi forces along the border, but this was later found to be false. A reporter for the St. Petersburg Times acquired two commercial Soviet satellite images made at the time in question, which showed nothing but empty desert. Holy Gulf of Tonkin!
Oh well, so Saddam gets his nose bloodied but was ultimately allowed to stay in power.
Fast forward to the next Bush, the son. Desert Shield which had morphed along the way into Desert Storm, is revisited in the 2003 Iraq War. Ridiculous tales of WMD and yellowcake uranium form a necessary but illusory pretext. Saddam Hussein is removed from power. Between 150,000 and 600,000 Iraqis are killed in the first four years of the conflict in a shock and awe bombing campaign.
The delicate balance between Shia and Sunni that the strong hand of Hussain maintained is forever broken. The Sunni Ba'athists, who have not been integrated into the new government go underground and start a counter insurgency movement. There is widespread sectarian violence. The conflict festers until 2011 when we finally withdraw, per an agreement that makes it obligatory to do so, an agreement authored and executed by President Bush.
Shia power in the region is magnified and the internecine conflict now spreads to Syria, Lebanon, Yemen and Libya, amongst other countries.
The embittered Sunnis become Isil or Isis or whatever you care to call them. The powerful Shia states start consolidating their power through their proxies like Hezbollah and Hamas.
Millions of refugees flee the region, many ending up in Europe and elsewhere, many fail to "get" the new culture and enormously tax both the economies and benevolence of their new hosts. Liberal politicians and U.N. Refugee officials start making ridiculous speeches and polemics about "open borders" and other utopian wet dreams.
People get sick of hearing about it and say "enough is enough." Hence Brexit.
Saddam Hussein was a simple guy, very secular as Arab dictators go. The Marshall Tito of his time. Hated but easy to understand. Give him a little mordida and keep his kids supplied with booze and porn and everything would go fine. Just don't cause trouble. The perfect despot for those spots in the world that can't function without a strong man to keep the villagers from ripping each other's heads off.
We monkeyed with a 1300 year blood war between Sunni and Shia and upset a very delicate balance of power and now the world is feeling the effects in spades, effects that are resonating in a horrific way right here in the United States and very strongly in Europe. And the sad fact is that the only thing they hate more than the west is each other.
See what happens when we get involved in places where we have no idea what we are doing and how badly we can screw things up?