I think there are three main factors that cause this, and it will take an entire generation to change things:
1) As the North American average waistline and body weight keep growing, so will the need for larger vehicles.
2) As the #1 consumerist society in the world, there's an ever increasing need for cargo space to carry all that stuff from the stores. I think more North Americans have garages full of stuff (crap) than garages with cars.
3) The public view of small cars and hatchbacks as being
girly versus their love for
my big manly 'Mmerican truck.
I think the fuel consumption and gas prices do not matter so much for the sheeple.
PS: as I walk my dog every evening through the neighbourhood I'm shocked to observe about 75% of houses have 2-3 cars parked in their driveways instead of their garage. In conclusion the word "garage" should be changed to "storage-space".