That's true, so why do we continually keep troops in danger in foreign engagements with no prospect of it actually accomplishing anything useful? Even when we achieve a realistic objective , like removing Saddam or the Taliban from power, we then remain in the situation and start pursuing unrealistic objectives that unnecessarily keep our soldiers at risk for decades rather than returning home after achieving what we set out to do.
The Middle East is a formidable tangle, particularly when the US government does not honestly address what the true interests of the regional players are.
First and foremost is the 1400-year-long war between the Sunnis and the Shiites. That war has been going on literally since Muhammad died. The Sunni-Shiite war takes precedence over everything else, as far as the Muslims in the Middle East are concerned. Everything they do has that war at the foundation. Everything else is a side-quest, the Sunni-Shiite war is central.
At this point, Saudi Arabia represents the leading Sunni force in this war; Iran represents the leading Shiite force. Syria, Iraq, and Yemen are all fields of battle in this war.
Assad in Syria is an Alawite, which is an Islamic sect allied with the Shiites. The Alawites are a minority sect in Syria that took power and maintained it by force against the Sunni majority. This is similar to the way the Sunni minority in Iraq took and maintained power over the Shiite majority in Iraq.
Turks are Sunni. Saudis are Sunni. They are both allies of the Syrian rebels.
The rebels against Assad are Sunnis. So that rebellion is actually a reflection of the Sunni-Shiite war, with the Iranian Shiites allied to the Assad regime against the rebels and Saudi Arabia and Turkey.
The Saudis also support an extremist Sunni Islam called Wahhabism. Wahhabi Sunnis are responsible for
ALL of the Islamic terrorism exported out of the Middle East.
ALL of it.
All of it.
The Wahhabis are so bat-guano-crazy that even other Muslims are afraid of them--you can easily Google for websites by Muslims of other sects that will tell you how crazy Wahhabis are, and that the Saudis are their primary support. The Saudis finance the spread of Wahhabism, primarily in the West. In masjids all over the US, Canada, Europe, in the prisons, everywhere.
ISIS is also Sunni Wahhabis. The core of ISIS are Sunni fighters from the Soviet invasion of Afghanistan, from the Chechnyan rebellion, from the Iraq War, and from every other conflict. There has been a cloud of 20,000-30,000 fighters who have no home, teen boys picked up and taught to be fighters, young men and now older men who have never been farmers or shopkeepers, men who know nothing but war.
ISIS are crazy-as-hell, and they scare everyone else, but they are still Sunni, and the Turks and Saudis will never honestly or effectively fight them, because ISIS is also fighting the Shiites.
But because ISIS is Sunni, the Iranians
are honestly fighting them. So in the Syrian war, the US is fighting ISIS, as are the Iranians (and the Russians with the Iranians). The US pretends that the Saudis and Turks are on our side, but they aren't. They are actually on the side of ISIS--or rather, they're not going to do what's necessary to wipe out ISIS, and they're not going to allow the Iranians to ever wipe out ISIS.
And the US has also been helping the Saudis fight the Shiite rebels in Yemen (who are supported by Iran). Essentially the US and Russia are both proxies of the Saudis and the Iranians in the Sunni-Shiite war.
So why is that? Why is the US a willing proxy of the Saudis? That goes back to 1972, when Richard Nixon took the US off the gold standard and allowed US currency to float against other world currencies. (Now, that can get into some conspiracy theories about the Fed and world bankers...and there might be some truth to that.)
But Nixon hedged his bet by making a deal with Saudi Arabia called the "petrodollar agreement." You can Google for it, but essentially the Saudis agreed to accept only US dollars for the sale of their oil to any nations. In order to buy Saudi oil, other nations must first buy US dollars. So that keeps the value of the US dollar artificially inflated against other currencies. In return, the US agreed to provide continuous protection and military support to Saudi Arabia. That is why the US rushed immediately into the Persian Gulf War when it looked like Saddam Hussein was going to invade Saudi Arabia.
And because the US is in lock-step with the Saudis, that puts the US in opposition to Iran far beyond what is necessary, because the US is just a sock-puppet (for the sake of money) for Saudi Arabia in the Sunni-Shiite war.