I would not be surprised if modern airliners do have the ability to couple the rudder and ailerons together. However, I believe the pilots would have to be able to dis-engage a coupled system in order to fight a crosswind on final approach.
For example: Lets say the pilots of an airliner (or any aircraft) are on final approach, and they have a quartering front crosswind from the right at an angle of 50 degress to the direction of flight. The pilots would have to either "crab" into the wind using right rudder (with a little left aileron input), in order to track the runway centerline, or they could perform a "forward slip" using RIGHT aileron and LEFT rudder (cross controlled) to stay on the rwy heading. I myself use both of these techniques to fight a crosswind during final...as do most pilots.
As you can see...in this example, the ailerons and rudder could not be coupled, they would need to be independent.
Perhaps an airline pilot in the forum can let us know how their aircraft works in this area.