Because of the need for self containment without hookups a very old technology- absorption- is used.
This isn’t the best for cooling, but a few things can help one to understand and maximize cooling.
If the refrigerator isn’t cooling quickly enough or reaching its usual temperature in hot weather, adjusting the thermostat won’t help. A thermostat simply turns it off and back on regarding the cooling cycles. In such cases it isn’t telling the fridge “I’m cool enough”. It simply can’t get cool enough.
Generally speaking the “first thing in the morning” temperature is the setting (provided it is working properly). That is the set temperature.
The larger the fridge the better it cools as a rule. Smaller units are often poor performers. Especially in tent trailers.
Ventilation, cabinet insulation, and at times an air flow assist fan can be first priorities.
Zero clearance on sides and top and minimal clearance at the rear, together with unobstructed flow through the top vent are keys, especially in sidewall vented units. Often times manufacturers do a poor job in the initial installation and the fridge should be removed, cabinet reworked, and reinstalled.
If you suspect such issues contact me for a step by step evaluation you can do at home.