What I do not understand is why the US is the military for wealthy countries like Saudi Arabia.
ISIS is literally at their doorstep, Iran on the other side and their solution is to simply purchase a nuclear weapon instead of drafting an army.
And now we are somehow enslaved to re-invading Iraq for a fourth time when it falls again.
Meanwhile our entire infrastructure of roads and bridges will fail in the next generation because we dump all our money into the war machine black hole so that the contractors can extract profit from taxpayers.
Why would Saudi Arabia want to do something about ISIS if it's cheaper to just invest in deterrence and pay other nations to get their hands dirty?
Besides, Saudi Arabia is a Sunni theocracy. ISIS is a Sunni (or at least Sunni-tolerant, judging by their behaviour) theocratic militia. They aren't predisposed to be enemies. ISIS has no religious reasons to invade Saudi Arabia and as long as ISIS doesn't kill Saudis, Saudi Arabia has no reason to intervene.
Iran is Shia but more concerned with Israel than with killing Muslims. In fact, Shia Muslims tend to be on the receiving end of Muslim intra-faith violence more often than not. The only reason we (the West) don't like them is because they tend to make aggressive moves towards Israel.
There's almost no reason to be concerned with Iran at all (relative to other countries in the region), if you're not Israel. On the other hand, Saudi Arabia is relatively non-hostile towards Israel and makes a great trade partner (especially for weapon exports).
In other words, there is a pattern here: most "terrorist organizations" (ISIS, Al Qaeda, Boko Haram, etc) are Sunni, most of our "allies" in the region (Saudi Arabia, Egypt, etc) are Sunni, most "bad guys" in the region (Iran's Khamenei, Syria's Assad, etc) are Shia. In fact, the only Shia terrorist organization I can think of is Hezbollah (from Lebanon).
I'm not saying we shouldn't be concerned with groups that want to wipe Israel off the map -- quite the opposite -- but we should be aware of who our "allies" in the Middle East are and who benefits when we intervene. The Shia/Sunni split is just one major aspect of Middle East politics and we're not even consciously aware of that one -- how equipped do you think we are to understand the situation in its entirety?
Saudi Arabia is hostile towards Iran and friendly towards the US (and therefore at least neutral towards Israel).
We like to maintain countries that are hostile towards countries that are hostile towards Israel for obvious reasons (enemy of my enemy, etc), especially if they are good trade partners.
The Saudis sell oil to us, we sell weapons to the Saudis, everybody benefits.
Well, except for the poor sods who have to live in an abusive theocracy, but we don't care about brown people, especially if they live far away from us.
I think there's a worry about some Al Queda / ISIS types taking over and causing havoc with the Saudi trillions. The Saudis may be undemocratic but at least they don't cause too much trouble.
But Saudi Arabia funded/funds Al-Qaeda and ISIS, they are Sunni terror groups, despite the fact that in theory, Saudi Arabia is a US ally. These groups attack Shias and other minority groups, not other Sunnis like the Saudis. Remember, a lot of the 9/11 hijackers were Saudis, and a lot of the funding came from Saudi Arabia. The US is funding its enemies by its strong links to Saudi Arabia.
You can read this article, or google around for better ones:
It's a very complicated relationship, I think the best long term outcome for the region and the world is a massive reduction in the importance of oil and the Middle East ceases to be important strategically.
They exported and funded their errant knights using those trillions. The main reason the Saudi government has been left alone by the more extreme elements in Saudi Arabia is that they are the main conduit for creating petrodollars, so if they were disrupted, the money hose might stop.
ISIS is literally at their doorstep, Iran on the other side and their solution is to simply purchase a nuclear weapon instead of drafting an army.
And now we are somehow enslaved to re-invading Iraq for a fourth time when it falls again.
Meanwhile our entire infrastructure of roads and bridges will fail in the next generation because we dump all our money into the war machine black hole so that the contractors can extract profit from taxpayers.