When everyone around you is in big trucks and SUVs, you're really putting yourself at a major disadvantage in a wreck if you are in something that small. I don't care how many airbags, how well it does in crash tests, etc. Sure, the crash tests can show that you're going to be fine in a collision with a wall, but test that little thing against an F250 from the side and see how well the dummy is. If you can live without your head attached, that may be the car for you.
I agree it looks like something fun to drive, kind of like a Miata or a Cooper S, but you would only find me in a vehicle like that in the mountains or on a track. I wouldn't risk my life by driving that around daily.
Just because something does well for Europeans and Japanese, does not mean it is well suited to America. We do have a different lifestyle, roads are different, surrounding vehicles are different, etc. Not to mention, over half the population is just way too fat to fit into something like that.