Congress and the president need to know what is going on in the world to know what treaties are sensible to enter into; to know who to support in civil conflicts; to know what foreign groups are potential threats; to know what scientific breakthroughs may impact our military and our economy and our health and safety. All of those things can have substantial impact on our national security - especially in the future.
The National Security Agency's task is to collect that information from signals, distill it, make sense of it, and report to Congress and the president when asked.
There are rules and laws about how that is done. There are procedures and checks to make sure that people don't break the rules. Are the procedures perfect? Obviously not - no system is perfect.
If we say the NSA cannot look at text messages, or call records, or anything on the Internet, then we obviously make those media free to those who do not want the US to know that information.
The laws and the courts say that the NSA is operating within the rules, and that when they have stepped over the line, they have been forced to get back over it.
The NSA has no interest in spying on Americans. It's not their job; they don't have a big enough budget or enough people to do it; and it would make their actual job more difficult.
Those who worry about "tyranny" in the US need to direct their ire away from the NSA and toward their local police who beat people to death or shoot them for no reason, the banking system with its usurious rates and over-the-top fees, and those in their state and local government who want to make contraception illegal, take away our right to vote, remove women's right to be treated as equals, legitimize religious and racial discrimination, and remove all of the social insurance that keeps us out of poverty when things go badly.
Direct your ire in the right place.
Don't be distracted by the "squirrel!!" of Snowden's document dump. Not while tens of millions are still out of work, tens of millions can't afford to sell their homes, tens of millions of young people are unemployed or under-employed while they have huge debt burdens, and tens of millions are without sufficient resources to be able to have a sensible retirement, and so forth.
I don't know what else to say....
My $0.02.
Cheers,
Scott.