the main driver of growth in the US before th GFC began was...

the main driver of growth in the US before th GFC began was consumers, as a direct result from housing

House prices were skyrocketing and Americans were refinancing and as the equity continued to improve with the value of their homes continually going up they were able to pay less in repayments and borrow even more against their 'valuable' homes

when the sub prime crisis hit and the full brunt of the GFC, home prices plummeted and all of a sudden, lots of homeowners were under water and struggling to make those repayments that at one stage they were reducing each month that went by

this is IMO the main reason why the Fed wants to inflate house prices back up, get the Ameican consumer spending again and lift them out of this slump