The only sense in which it is "theirs" is that they took it away from us in the first place.
In the civilized world, things don't belong to people because of their blood-they belong to people who create or buy them.
We found the oil (after discovering and developing productive uses for it), we created the means to recover it, developed a transportation and marketing system for it, and designed, produced, and installed the infrastructure which keeps it flowing.
After which the Saudi Arab barbarians, who design and create nothing, stole it from us.
Now, admittedly, we acquiesced in this rapine because of the degenerated nature of our political system, preferring instead to accept Saudi bribes to politicians in exchange for continued access (at their prices).
However, by any rational definition of ownership, it's our oil, not theirs-and I see no problem with taking it back.