Our force is kept deliberately small in the hope that it will be less offensive that way. Most of them are support personnel for command and control, and air operations. We do not have a lot of the ground troops that would be needed to hold a base deep in hostile territory.
In other words, the current situation makes it relatively easy to capture our military personnel. The many American civilians in Saudi Arabia would be even easier to capture. The potential human shield problem is real.
If we are going to fight Saudi Arabia, we are better off if we have withdrawn the potential human shields first.
BTW, we do not yet know how things will go in Saudi Arabia. The House of Saud still has a chance to come to its senses. But funding terrorism has to stop, or it will mean war.