I do not think God is blessing America.  America is set up as a secular society, and the people are just living for material happiness.  God's blessing is not reflected in the accumulation of material goods if those goods just distance people from God, which they do, and God does not bless a country that does not actually recognize Him as God.  Just the fact that we are a secular nation means that God would not bless us, because we are not recognizing Him as the one who would bless us.  If anything our current success could be a curse, because our success seems to take us further from worshipping and interacting with God.