It is possible that you are right. Saudi Arabia may have to go through a stage of control by Islamic fundamentalists. If so, 70 years of American support for a corrupt and venal monarchy will have played a large part in provoking this. In any case, it is their country and their problem. Just an Iran is starting to throw off the shackles of theocracy, so too will the Saudis one day.
American interference in Afghanistan was pretty much non-existant prior to its invasion by the Soviets-- and even then, the money we sent was funnelled through the Pakistani intelligence agencies because we wanted plausible deniability. Anyway, people who argue about how wrong we were in Afghanistan are just like the people who argue how wrong we were to support South Vietnam. Interestingly enough, all of the actual South Vietnamese immigrants to this country that I know think our only sin was to desert them. I agree with them. Our fault in Afghanistan was not that we supported those fighting the Soviets, but that we pulled out and left them to be preyed on by their Muslim neighbors.
I'm not aware of anything we've done in Iraq, other than stomp them out of Kuwait. Likewise, I don't think we've done much of anything in Syria. Jordan is another case, though: haven't you seen their young king on television? Very reasonable, very moderate, British-educated, and very interested in advancing his country into the modern age. Seems like pretty good western influence to me.
As for Saudi Arabia, you may think it's just fine to abandon them to two generations of Islamic fascism, but besides turning their lives to misery and creating a flood of refugees into the west, I think it's likely to make them more virulent sponsors of international terrorism than they already are. Bad idea, in my book.