It was nigh impossible to intervene in Saudi Arabia after 9/11. Iraq bankrupted itself in its 8-year war against Iran, building itself a huge-ass military and going into debt, which scared the rest of the gulf countries, then proved their fears true by invading Kuwait and thus isolating herself, and consequently blundered hard by having its military destroyed by the U.N. alliance (lotsa infrastructure destroyed too that was super demanding to rebuild since Saddam wasted all that money on his military), Iraq then had a decade of sanctions and no-fly zones before full U.S. intervention; the 2003 invasion was launched through Kuwait and North-Iraq/Kurdistan. Saudi Arabia on the other hand…was integrated economically and politically with the rest of the Middle East (other than Iran), bordered 7 Middle Eastern countries, was a major supplier of oil to many countries (14-17% of worlds reserves), and loaded with probably a trillion of U.S. petrodollars. For an invasion of Saudi Arabia…Kuwait (the staging ground for Operation Iraqi Freedom) would be opposed, since its also a monarchy and staunch ally to the Saudis. Egypt was also a formal but long ally and benefitted greatly on Saudi oil money remittances and investment and would not like all that to go to ruin via war. Yemen was neutral in 2003, Oman was a Saudi ally, the UAE was a Saudi ally…Lebanon and Palestine were close Saudi allies, back then even Syria was a formal Saudi ally. Assuming it’s the U.S. and U.K., they’d need to convince Qatar to be the odd one out and go against the entire Middle East by having the U.S. stage ground there like they did in our timeline in 2003, which at that point the Qatari government would probably not do out of Arab patriotism from their population and the fact they’re a country of 700k people and are land-locked to Saudi Arabia. Assuming America just airstrikes for months (and have all their embassies kicked out of every Middle Eastern country) they’d now need to invade the country that bears the holy site of islam as Osama bin Ladin predicted, and boy will the Saudis play up that rhetoric and go nuts with those petrodollars and create who the fuck knows what kind of monstrous terrorist and insurgent groups with all that money flowing in the region that’s hostile to the U.S.. We’re not even getting to the occupation yet. The entire concept of a Saudi intervention post 9/11 would only work if the U.S. did not stop Saddam from annexing Kuwait, then if a 9/11 happened they could try jointly invade the Saudis with Saddam’s army or smth as a staging ground. We could go really back and assume by not sacking Iran’s leader in 1951 they’d prevent Iraq and Iran from going to war, and consequently if a 9/11 happened they’d have more allies in the region and a better political climate to shut the Saudis down. But our timeline? No, that would’ve been disastrous, almost Putin-like or even worse.