Any system can be explored with CLDs.
There are a number of ways in to starting a CLD:Stories, Documents, Preliminary Diagrams, Brainstorming Variables, Stakeholder Needs, System Needs, Behavior Over Time Graphs, Critical Loop.
There are lots of other types of diagrams and representations of systems including textual narratives and documents.
We strongly recommend building each CLD one node at a time getting the simple parts right as you go. It may not matter much where you start as long as you keep going. The system will reveal itself.
We see systems more clearly when we pool our experiences. See Perspective Matters Feeling an Elephant Blindspots
Do we have the right people in the room?
See Cave Drawings and Campfire Conversations
See Causal Loop Diagramming for a list of tools we can use to create CLDs.