Why exactly do you want to get rid of them? And who do you propose to put in their place?
The US certainly doesn't want to "get rid of them". Because of the fact that the wahabbis would take power, in that, you're absolutely correct.
However, it will never happen. Because there's like 27,000 members of the royal family.
Wahhabism is already in control of Saudi Arabia.
You need to read a bit about Saudi Arabia. There is a delicate power balance between the fundamentalists and royal family.
There is a power balance between the political and the religious, but the royals are Salafi. Wahabbi.
Don't believe that there is a difference. There really is not.