Culture Differences

After I went to osu for an exchange in Autumn 2008 during my undergrad I came back for grad school in September 2009.
During my first stay I recognized several cultural differences between Germany and the US. 
One of the most important differences was the low consciousnesss of Americans about sustainability and environmental awareness. Why is there such a big gap? How can one change peoples behavior? How visual communication design support a change?
These questions were the basis for my application to grad school...