Falconeasydriver
This is probably piolitically incorrect, but sometimes someone has to become Devil's advocate
Iraq is a battlefield with many different actors fighting on it. It wouln't be should GW Bush have not decided to invade it. Now, US should not complain about Iran or any other ME power destabilizing here or there. If they don't like it they should go. Well, that is what they are doing. And they will also leave Afghanistan, eventually. Both of them big mistakes. US can only withdraw or genocide those countries. Nobody expects the latter from the first democracy of the world.
US can preemptively bomb a country (with more tons of explosive than during the whole world war only to find out there was no reason for the attack because there were not mass destruction weapons) and occupy that country for 8 years but Iran can't "destabilise" it?
There is only one usurper of US/saudi relations: Israel. As put by Mearsheimer and Walt, the hawkish policy of Israel and US has been very bad for both countries interests. So much so that today it would be ten times more difficult for the US to gather the international support and legitimation to make a preemptive attack on Iran, if that was US intention. Probably they would prefer an israeli attack. As for Israel, ten years ago was in a relatively stable situation. Now the situation is highly volatile, which is never good for Israel. Israel is a country with no margin for error in matters or war. They shouldn't be so trigger happy.
The world, and particularly the ME looks now like a chess board after many movements without "casualties", crammed with the deployed pawns, bishops and horses. Any time the fight can begin and leave the board half empty. Too many years of post-cold, cold war. Too many preparations. If something triggers the fight, hell is going to break loose.
If the Israelis want to bomb Bushehr, the Saudis will open the sky for them, that is for sure. US is arming both with brand new fighter bombers, including stealth ones. But what would happen then?
If the iranians surprise every body with nuclear bomb tests or something like that, what would happen then?
If the iranian regime was overthrown... Well: this is not going to happen so I won't bother to speculate about that. Too good to be true, but not even the CIA, mosad or any other can do that.
GW Bush screw it totally and now the world has to choose between to evils. a nuclear Iran or...