The reality is there is lots of range loss when using the cabin heater, which obviously one is most likely to do when cold. All modern Tesla's use heat pumps for cabin heating, which ~halves the range loss, but it's still substantial.
I have a 150 mile round-trip commute when I need to go in to the office. My "summer range" (really more "not-winter range") is 240+ miles. I stick to posted speed limits for efficiency, 60-65 MPH. This winter I've been getting back home with 30 miles of range to spare. I haven't done the math or recall what power draw my gauge cluster reports when I toggle heat on/off, but I do remember it reduces my range estimate by ~5 miles when I turn the heat on.
Usually it's only pulling that much juice for the beginning of a drive and after a few minutes it reduces when it finds a steady-state.
2kW is about the same amount of juice that the drivetrain pulls when driving 35mph, so it can make a pretty big difference in the efficiency of shorter drives.
Sidenote: even though resistive heating is less efficient in heat per watt, using the heated seats is usually more efficient in terms of comfort per watt than heating the entire cabin
How are you getting "fraction of a percent of what is needed to move the car"?. Wikipedia says the model 3 (long range, RWD) has 82 kWh capacity and 363 mi range. If you drive at 40mph that's 9hrs of driving, meaning the car consumes 9kW at that speed. 1kW is not "fraction of a percent" of that.
Today, it's closer to 1.5kw, all-in, accounting for heat pumps, etc.
Cooling is less intensive.
Keep in mind: Homes are also often well-insulated, at least, much more so than a car. Most car insulation is designed for noise/etc, not for temperature control. The glass is usually R-1 or worse.
So if you want realism:
My wife's office, no more than 150 sqft, built in 1923, and with no real insulation in the walls (and no space for it), and a bunch of older windows, can't be kept at 68F by a 1500 watt space heater running 100% of the time on a cold day (IE 30deg F).
This is in GA, so not exactly a super-cold climate, eiher.
Meanwhile, my workshop, same property, built a few years ago, 2000 sqft, and amazingly well insulated, can easily be heated/cooled to 72F by a 1.5kw minisplit running basically never.
Mine doesn't have a heat pump, so I can definitely notice range decreases. Also consider that the battery likes to be at a good temperature, and that isn't going to be free if your car is parked outside for 8 hours. That changes range too
It's not the same as an immobile insulated house.
2kW in the civilized world.
Tesla's used to, not sure if they still do, had a four way valve that could be used to route coolant around the system in the right direction. High wear and failure rate part.