The real reaction of the American public isn't the talking that happens now. Or the next month. Or the next year.
It's that people like me, who are young and have decades of time we're going to put in to society - working on infrastructure, working in the military, working in civil service jobs, etc - have this information and have someone like that as a counter point to the obvious corruption happening in government.
I'd wager the biggest effect of Snowden - because anyone watching suspected much of this anyway - is going to be the legacy of someone who stood up and said something about it, screw the cost.
Rolemodels like that are important, especially amid a context of massive social and governmental breakdown.