What is overheating my car?

The interior of the car or the engine specifically is steaming? If it’s the engine, the likely coolant isn’t being circulated properly. Possibly sometime as simple as air in the system that needs to be bled out. Or maybe there are blocked oil passages and oil isn’t flowing properly, also leading to added heat not being removed. I’d go with coolant being more of an issue. Water pump may be something else to look at. If it’s not pumping properly then clearly that’ll be an issue. As a test, you can run the engine without the rad cap on but only do so when the engine is cold. You should see coolant circulating (unless you can see it from the reservoir tank).