My 2011 Lacrosse has an Atwood WH and does NOT have a switch outside on the heater itself. It also does not have an anode rod. I have a switch panel in the TT with an electric and gas switch with a red light between them (wish I had a photo handy for you). The red light only comes on when there is NO propane present at the WH.
My 2009 Wildwood had a Surburban WH and DID have the external switch. And it did have an anode rod. The inside switch panel only had 1 propane switch and the red light.
Both had a breaker in the converter panel also.
Hope this helps on the difference between the two makes of WH (at least the newer models, older models of each may be different altogether).