You're listening to your own engine yes, but a car control system presumably has more direct access to that information. You simply can't hear sound from outside - and car makers advertise this as a feature! - to say nothing of the fact that many or most drivers will be playing music by one or another means.

You can hear plenty of sound from the outside, most of it in the lower frequency bands and sometimes only via bone transmission, but it's there. Get a pair of active noise-cancelling headphones and try it for yourself, especially in more complicated driving situations.

While the brain can still operate a car with the loss of some input, visual input isn't really enough and is heavily supported by all other senses (acceleration and gravity, sound, touch and vibration, temperature and kinesthetic). Unlike modern computers, the brain is massively parallel and asynchronous, so it can simply use all of the inputs to find the correct course of action, even going as far as considering multiple lines of thoughts (and then your memory is manipulated so you only experience the chosen line of thought, similar to your vision being manipulated when you blink).

You are also blending sounds from other cars, as well as sounds from your tires on the road which gives you some feedback on the driving conditions. All of those match patterns that you have seen before and give you a better feeling about your car status.

The brain is using hundreds of different captors and is order of magnitude more powerful than any computer today. Attempting to drive with a couple cameras as only sensors is a recipe for disaster as has already been proved (see also: Tesla crashes)

Same here, tried it with earbuds once and it was very unnerving. Took them out after a minute.