I own a 1992 two wheel drive Chevy Blazer with almost 100,000 miles on it. When I let go of the steering wheel on a straight road it pulls significantly to the left. After checking the air pressure and then having the tires rotated, there was no change. So I brought it to an alignment shop where they said bushings had to be replaced in order to do an alignment. My question is can worn-out rubber bushings cause a pull and make an alignment impossible?
In order to do a proper wheel alignment on any vehicle the front suspension should be inspected and all necessary repairs performed. Some common wearable metallic parts are ball joints, tie-rod ends, idler arms, etc. Then comes the family of rubber suspension parts: upper and lower control arm bushings, sway bar bushings, stabilizer links and so on.
A wheel alignment is based on three different angles that the suspension is aligned to; these angles are called Camber, Caster and Toe. And they affect stability, tire wear and whether or not the vehicle will track straight down the road.
Getting back to your question, yes, a worn out bushing can cause a pull and make an alignment impossible or, let's just say a waste of time. When an alignment is done correctly on a front end in good condition (tight), these angles are set to manufacturer's specifications and they will not be altered by normal driving. On the other hand, if the angles are set with worn-out (loose) suspension parts, the first time you hit a bump or make a hard turn, those unsecure parts are going to shift and the angles which were just set are no longer even close. In addition, a worn-out suspension part which breaks can possibly cause a loss of control while driving.
In your case, the mechanic is probably referring to control arm bushings. These parts will have a definite effect on alignment, since they are the final link between the suspension and frame.