Imagine we do some silly things like 'print' (not how money is made, but that's another topic) countless billions to trillions of dollars to pay for things we can't afford, such as pointless wars (not really pointless - Iraq/Libya/Iran all moved to of settle their oil for currencies outside the dollar, as Syria and Venezuela have now also done) or to inflate the stock market by injecting money into it resulting in inflation and calling that 'growth'. Or imagine we grew so deeply in debt that our only ever chance of possibly paying off old debt was by taking on ever more new debt in a cycle that seems to have no possible happy ending. These things might normally have an effect on an economy or currency's value or stability. But with the petrodollar if the value of the dollar goes down, this incentivizes other nations to further increase their holdings of USD to ensure a stable access to a certain amount of oil. And, like magic, the massive quantities of money start being removed from the market and tucked under the national bed's of a variety of different governments. The petro dollar means we can basically do whatever we want economically, and the rest of the world has to take it, while smiling.
This is why Saudi Arabia is able to flaunt their position. Do you remember Majed Abdulaziz Al-Saud? Neighbors saw a bleeding crying woman fleeing his mansion in Beverley Hills. He'd engaged in rape, assault, various forms of drug use, and all other sorts of fun stuff. Our response? He was released on bail and then, lo and behold, simply flew back to Saudi Arabia, and then it just disappeared from the news. It's the same story here. This is really big news, and this is something that the media and politicians could completely cripple Trump with. Yet, for the first time in his two years in office, they're remaining relatively reserved. The reason is that we need to make a big deal of this, and ho and hum about what should be done. But in the end, I think the chances of us doing anything, beyond token gestures, are basically 0. If we became enemies with Saudi Arabia, it would be a a potentially fatal blow to our economy, as it would mean the immediate and utter end of the petro dollar. Granted that dollar is already dying, but it's dying a long, slow, and protracted death. This would be self decapitation by contrast.
Even the good old 'regime change' or 'bringing democracy' isn't the same with Saudi Arabia as with the rest of the world. From a PR perspective Saudi Arabia has Medina and Mecca. They would be able to successfully spin the invasion as an attack on Islam. And Saudi Arabia also has extensive military forces. In spite of being a relatively small nation they are the third largest spender in the world on their military, and spend some 10% of their GDP exclusively on military - we only spend about 3% by contrast. We can't invade them and we can't really turn against them. We're the most dominant nation in the world, but Saudi Arabia is our Achilles' heel, and they know it.