The average American doesn't realize how usefull these little boxy cars are. I mean it's great driving around in my xB knowing passengers in the back have more leg room in my car than in a Suburban. And I get more than twice the mileage.
Not that it isn't allowed. These cars fit a certain type of buyer, a buyer Toyota found with the xB. When the desire for these comes around a bit more, it'll happen. Remember back in the 80's? Remember how the American companies had to redesign all their cars to be fuel efficient and such? It'll be like that. We just have to wait.
I've looked into importing a Cube last year and they are pretty inexpensive. Where you get killed are the duties and shipping! I know that you can import into Mexico to bypass duties, but not sure what the process of importing from Mexico to the US!