Why can’t you have N cables supplying power to N cells in parallel?
Just to be clear, you'd ordinarily have the cells themselves in series or a bunch of parallel groups in series to reach high voltages, and as far as the charger is concerned it's just one big battery with a single positive and a single negative terminal.
On the other hand, if you're suggesting balance charging where you have an individual connection with the charger between each cell, that's not really practical to do with large batteries because the current would be very high and the voltages very low, which, as far as cabling goes, is the worst-case scenario. Charging a single cell at 100 amps and low voltage requires basically the same size cable as charging a bunch of cells in series at 100 amps and high voltage. If you need a big, thick cable for each cell, that gets unwieldy very quickly.
Another unpractical option is to switch the battery into a single parallel group during charging and charge the whole group as if it was a single low-voltage high-amp-hour cell. That's unpractical for the same reason; low-voltage charging is an inefficient way to move energy around. Also, switching from series to parallel would require a lot of high-current contactors (basically, electro-mechanical relays), which are kind of expensive.
By comparison a normal 200HP engine at 30% efficiency is producing 667kw of waste heat into the air with a tiny percentage of that going out the exhaust pipe.
This isn't really a fair comparison. Cooling capacity goes up with the temperature difference to ambient. It's a lot harder to cool 8kw of heat at 20C above ambient compared to 8kw at 200C above ambient.
The majority of that heat is removed via the radiator which uses a liquid coolant which should not exceed 105C even when the outside temperature is 45C so that’s only 60C of wiggle room.
Though it’s a fair point batteries have lower maximum temperatures, at worst reducing charging rates when outside temperatures exceed ~(110C or 43C) is hardly deceptive or particularly relevant to most people. High end cars could even use the car’s AC in extreme situations.
An average ICE is only producing 200HP at a specific RPM, for short period of time. Red-lining any sedan while being stationary will probably overheat the engine pretty quickly, as the on-board radiator fan either electric or mechanical will not provide enough airflow. They are designed to be cooled by incoming air while driving.
With electronic ignition, you usually have a way to limit max RPM by stopping ignition, so you're not producing work (and heat) either way.