America could initially freeze and then seize most of their assets in the US and even take control of most of them in Saudi Arabia as they did in Iraq. In fact it could probably claim a portion of those assets by accusing Saudis of causing 9/11 and sponsoring terrorism for which there is plenty of justification. It could further accuse them of violating human rights by killing people like Kashoghi. If America decides it no longer wants to support the Saudis, it will take a New York minute to covert them into enemy #1.