Hmmmm... Must be a function of the surface area exposed to direct sunlight, outside ambient temperature, the size of the RV air conditioner, and the inside volume of air being cooled. Our 19' Bambi has never had problems cooling down, even in 110+ degree heat.
Last summer when our home heat pump was dying, we spent a couple of days in our Bambi in late June and again in mid-September, waiting for the air conditioning repair tech to come. On both occasions, the daytime highs were 105-110 degrees; and the air conditioner in our Bambi never had any problems cooling it down to around 75 degrees. However, we do NOT have panoramic windows, and we cover the side windows and ceiling vents with auto shade screens.
Since 2005 (when we bought our Bambi), there have been several occasions when we stayed in our Bambi instead of imposing on relatives and neighbors when we had problems.