And they do drive Teslas outside the US as well.

And should there be places, terrains, urban conditions etc. that Tesla doesn't cover, they will see it and can hire a number of chauffeurs to drive around there. Even if they hired 1,000 drivers to gather data in certain geographical areas at certain hours or weather conditions that they lacked input from it would be a drop in the ocean compared with the cost other car manufacturers face to keep up with Tesla now.

You can't just install autonomous driving systems in any combustion engine car without changing lots of systems. Tesla is electric fist. Everything is already wired, ready to be measured and in feedback loops.

Sure. I am mostly wondering about the demographics of Tesla owners. My guess would be that people who own Tesla cars tend to live in similar areas, with comparable lifestyle. There is also the case of driving style. I doubt there are people that tend to drive like my grandmother, and I would assume that a variety of driving style is important as well.

All I'm saying is that the claim of N million miles should be taken with a grain of salt as long as you do not know the entropy that these miles contain.