People don't seem that outraged because of the enormity of what they have been faced with.
The size, scale, scope, and capability of the NSA domestic survellance programs literally surpass the wildest dreams of secret police organisations like the Stazi. Snowden's revelations have dropped an undeniable bombshell on the US public, which despite its best efforts to ignore, not even the mainstream media can completely hush up. American's now know that they are under 24/7/365 complete and total government survellance each and every time they go online. Everything they do is monitored, recorded, and kept on file for the rest of their lives.
It takes time for a human being to fully come to terms with something like this.
For American's, it will taken even longer. The idea of a free America is still a very powerful one. The idea that certain things don't happen in America is a founding principle of the nation, and the reason why so many millions chose to build a new life there. The idea that a secret police -- the most quintessential aspect of an oppressive state -- now exists in the US on a scale never before seen in human history is an idea in fundamental conflict with American's own national self-image. It would be easier to accept that the individual states never actually existed than to accept this.
But facts are stubborn things. Despite all efforts to smother it, this story is not going away, and American's are not going to be able to ignore it. This is too huge. The NSA and it's programs are a sledgehammer, slowly pounding at the very foundations of the US itself. No matter how asleep, how apathetic, how cynical, or how uniformed you are, eventually the punding is going to wake you up too.