I am a UK operator and have no experience nor knowledge of what happens in the USA. That said, I would be surprised if our philosophies concerning MELs were different.
The MEL lists those deficiciences or unserviceabilities with which an aircraft can be flown and under what conditions they may be carried. Fundementally, these must not affect the airworthiness or safety of the aircraft. For that reason, it is unlikely you will find any MEL entries covering the structure of the aircraft, landing gear and engine. Clearly, with these items not listed, one would not dispatch the aircraft with these sorts of deficiencies.
Basically, if the flight is being operated under rules that require the use of a MEL, and the item is not listed, then it must be serviceable.