I'm not American, so my education with regards to governments did not include specifics of how the US government works, only a general overview of the governments of most countries.
I'm aware that the US government is not monolithic and homogenous. But it's things like the NSA's programs (such as PRISM) that centralize resources and funding, and turn a heterogeneous government into a coalition defending not always what's best for the nation and the world, or defending the interest of a small group to the detriment of non-adversarial groups with less influence.
Past behavior isn't a guarantee of good future behavior. The NSA always had a fairly good image: secretive but inoffensive, mostly concerned with breaking encrypted communications of interest to national security, and offering good crypto for American citizens and companies. It didn't have the less nice overtones the CIA has, for instance.
Well part of that is how the NSA's mission. NSA is charged with both defense and offense. Defense side has brought us AES, SHA1, etc. etc. Offense side is well... the current controversy.
Anyway, your words are unfortunately generic, and can be applied to any federal government agency. Centralizing resources is almost always going to be either more efficient or more effective. It is important that the NSA is technically a military organization (with tons of civilian supporters). It is run by a 4-Star General, and their primary targets are military enemies. It is imperative for the NSA to be as powerful as possible from a collections standpoint.
The key therefore, is in the laws that restrict the NSA's behavior. The NSA is an outstandingly useful tool to the military... run under the same executive branch that the rest of the Military is run (Department of Defense). Unlike the CIA, which competes with the DoD for budget material, the NSA is most certainly a military tool.
A nation's citizens need to be comfortable with its military. Squadrons of F16s are almost never deployed against citizens, and the massive war machines (Fleets of Carriers, Napalm, etc. etc.) are similarly not to be used against one's own citizens. The NSA is on that list of extremely powerful, but useful tools of the Military's toolbox.
I'm aware that the US government is not monolithic and homogenous. But it's things like the NSA's programs (such as PRISM) that centralize resources and funding, and turn a heterogeneous government into a coalition defending not always what's best for the nation and the world, or defending the interest of a small group to the detriment of non-adversarial groups with less influence.
Past behavior isn't a guarantee of good future behavior. The NSA always had a fairly good image: secretive but inoffensive, mostly concerned with breaking encrypted communications of interest to national security, and offering good crypto for American citizens and companies. It didn't have the less nice overtones the CIA has, for instance.