I actually agree with almost everything you've said. America is not responsible for the ME's ills. However, I do think that many states in the ME are classic client regimes, much more interested in keeping foreign sponsors happy than their own populations.
This creates a very strange and perverse set of incentives, where the US is incentivised to back their clients, even while the clients are essentially destabilizing the region.
I would assume[1] Saudi Arabia doesn't fund terrorists that aim to topple the kingdom. I do think that terrorism and instability is most common in states that don't have strong civil institutions, a civil society capable of mediating disputes.
Client regimes are already toxic to civil institutions, because at the end of the day, they don't need a very broad platform of civil support when their primary source of power comes from abroad. By propping up bloody-handed dictators, the US basically ensures that whatever replaces them will be worse - because the dictators are so damaging to the kind of civil society that would allow for a peaceful transition into something better.
I'm not saying that America is responsible for this. Probably if they withdrew support for Saudi Arabia, some other power would fill their shoes. I am saying that they, and nations like them, are inevitably powerful forces for instability in resource-rich, strategically important regions like the middle east. America is particularly bad because their policy is so inconsistent - one moment, it's about US strategic interests, next, economic, next, it's about exporting democracy and protecting human rights. So they prop up somebody like Saddam Hussein for years, then they sanction Iraq for years, then they basically demolish his entire country and state, and somehow expect this completely savaged country to gin up a functioning government from literally nothing while fighting a civil war. Their involvement in Afghanistan was even more insane.
[1]: It's impossible to be sure about this kind of thing. In the Russian Revolution, government funded terrorists blew up the minister of the Interior, for instance. Even a functioning state is pretty far from monolithic.