Gravity, I see Tesla working first to pick the low-hanging fruit and then coming back later for the harder work. The low-hanging fruit right now is in countries with pent-up demand for Model S but no previous ability to buy. China is such a place right now, and the development of a right-hand drive frees up cars for other markets such as UK, Australia, and Japan. US sales of Model S look less robust than you would normally like to see for several reasons including the approaching release of Model X, which is already taking away some Model S sales. Remember that Model X will be the newest Tesla and the one that raises the most eyebrows next year. Meanwhile, the US supercharger network keeps growing, and as it grows the practicality of owning any type of Tesla grows. Europe may be a better location for supercharger saturation before the US because of population density. While Tesla is restrained by battery supply, it makes sense for Tesla to branch out into other markets and set up the infrastructure for models that will follow. Should Tesla become demand-limited at some point, it can advertise and work harder on the sales, but right now there is no need for such behavior. When there is advertising, it will enhance the word-of-mouth selling that Tesla owners are doing right now.
To a large extent, the purpose of Model S and Model X is to take us profitably to Model E. While there are finite limits to the number of cars you can sell in the $70K to $110K range, the number of sales in the $35K to $45K range is hugely larger. Even if the growth rate of Model S sales in the US has momentarily flattened out, and I am not sure that it has, Model S and Model X will take Tesla where it needs to go to enable Model E. Remember that the US is full of people who understand BMW and Mercedes cars, but a large percentage of high-end buyers have never looked closely at a Tesla. I believe I sold a Tesla to a high-end buyer this weekend, who drives a Lexus SUV. He has heard of Tesla but had never sat in one. Now he has and he wants a Model X. I'm thinking that fully half of potential Model S buyers in the US are holding out for Model X now. That issue alone will greatly affect Model S sales in the US.