For both the engine & catalyst, I wouldn't be worried about overheating; I'd be worried that critical parts would become too cold from an extremely-extended, overnight idle.
In the case of the engine my concern would be low cylinder wall temperatures and low oil temperatures, leading to a risk of oil degradation from unburnt fuel and from combustion-produced water vapor having an opportunity to condense in the crankcase ventilation system.
WRT the catalytic converter I'd be worried that it would become too cold during the idle period, dropping below its activation temperature, and then overheat when the vehicle is driven away due to accumulated particulate matter (insufficently-burnt fuel, etc.)
The difference between a prolonged idle, and stop-and-go traffic is the "go" part of the traffic situation. The engine periodically gets placed under load, helping to keep the components and fluids at their operating temperatures.