What's exactly the reason why so many Americans drive Automatic cars?

Apparently 90% of all Americans drive an automatic car. And only 15% of Europeans drive an automatic vehicle. As an European, I don't get this. Why do so many Americans choose to drive automatic? I asked my dad his opinion on automatic vs manual. He has 2 cars, one's an automatic, and his other car is for work, and has a manual transmission. So I ask him which one he likes better. He says that it really doesn't matter a tiny bit to him. He says that he doesn't even notice a difference because he's so used to shifting gears himself. I think most other European drivers would say the same: That it doesn't matter. So why do Americans choose to drive an automatic so often? I don't think that the answer is as simple as: 'oh it's just easier' because then we would also be driving automatics more often. But that's not the case.