Sure, it can be done. But a lot of people including me simply will not put their kids in a 2 door for safety concerns. If my car is on its roof or side or sinking or one side of it is smashed closed, I want maximum quick egress options.
But more to the point, once your kids are old enough to have friends and a sense of a little independence, you will be carting them and their friends all over creation to all kinds of activities. Sports, school, play dates, day camp, day care, birthday parties, movies, outings, weekend trips, and on and on. If you have two kids, having seats for 4 kids means not having to take two cars, and it means you can carpool with other families, saving each other unnecessary trips. That cannot be understated. Don't forget the front seat is not an option until they reach a minimum weight; in Maine, 100 pounds.
Our kids are 5 and 8 and the 5 year old isn't quite to the point of wanting to have a friend along very often, but when she is the Outback will be too small. When I was a kid we used to pile in the "way back" of the Malibu station wagon, but those days are long gone.
So, I'm confident the statement "most Americans don't need more than a 2 door commuter car" is false.
Now, personally I'd be willing to have a family truckster in the garage and commute on a motorcycle or scooter, but it's not usually feasible because usually I have to do drop-off or pick-up on my way to/from work. My moto hasn't been out of the garage yet this year. :(