Have you found the Converter? That's where it should be. The Converter, besides transforming AC power to 12V DC power, passes the 120V AC power to all the AC powered appliances and outlets. The circuit breakers should be where that power supply is split up and distributed - the Converter.
In my trailer, the water heater is very close to the fresh water tank, which is logical, since it's output has to go through the water pump. The Converter is at the other end of that space, which makes sense too - it should be away from a "wet" area.
The Converter in my trailer is not IN a cabinet. It is behind a black metal panel that is fully exposed and is below the couch.
- Jack