We can safely say that Saudi would not have embarked on its Yemen conflict without first informing Uncle Sam and getting Uncle Sam's approval. The Saudis would have explained that the whole point of them going to Yemen would have been to stop Iran from creating more trouble - this would have been music to the ears to some in U.S. government. It remains to be seen how long will Saudi and its allies be willing to stay in Yemen if there's no end in sight. Them packing their bags and leaving without achieving their objectives would be a major loss of face and would be a victory to Iran.
Same thing in Syria; if Assad is still firmly in power in 2-3 years from now will the U.S. still sing the same tune or will it change its policy? Will it acknowledge that Assad is there to stay and that U.S. backed rebels have failed to produce the desired results? How much influence will Saudi play in determining how the U.S. carries its policies towards Syria and Iran? If there is indication that the U.S. is willing or is forced to seek some level of accommodation with Iran [based on realpolitik and logic] will Saudi and its allies - together with Israel - create mischief?
