It seems more likely that an inability to work with multiple "regions" is
due to inadequate instruction in system/surroundings in the intro physics
course than to too much. As John Clement commented, few intro physics
textbooks say very much about system/surroundings. Closely related common
failures are not analyzing processes with different choices of system,
ascribing potential energy to single objects instead of to pairs of
interacting objects, and confusing pseudowork with work, with associated
errors in dealing with the energetics of deformable systems.