If you lose posture in your golf swing, there can be many causes, but the causes will fall into one or more of these three categories -- technique problem, physical limitation, equipment issue.
Let's talk about the physical limitations, which can be categorized as either a medical or a fitness problem. As a player, you yourself will NOT know what your swing characteristic's cause is, or which category your cause fits under.
You need to find a TPI Professional at http://www.mytpi.com/find . Ask your TPI Professional to physically assess you and then refer you to the correct treatment, coaching or fitness routine.
If you're talking physical limitation then yes a deep squat could be a reason. But, the MAIN reason is poor technique-ie poor posture at address and pushing off the right leg on the downswing. Keep the bum back at address with a neutral spine and pull off the left hip/leg in the downswing and continue to rotate post impact.
Tourswing 2 weeks ago