The United States has various institutions and organizations whose purpose is to protect the country and maintain the status quo. Given the rising degree that nations are becoming interconnected with each other along with the rapidly increasing evolution of technology, a country such as the U.S. rightfully needs certain institutions to protect itself. The scope and range of threats that exist in the world today are too great for a country to manage solely by the office of the president. However, while we do need and appreciate the services that these institutions provide for us, they are motivated by self-interest the same way that any living or somewhat autonomous system is. It is therefore not too great of a mental leap to acknowledge that these institutions work to sustain the very threats that caused their inception, to ensure their own continued survival.
This concept is somewhat linked to the evolution of a state itself. Prior to World War II, the U.S. was not the world leader or hegemon as it is known to be today. Thus it was not as involved in the affairs of the rest of the world to the extent that is has grown to be, and thus it was at a lesser risk of threat from foreign actors and nations who were more or less left to their own devices. The lesser degree of available technology was certainly a factor to this end as well. But after World War II it became evident that the U.S. had a greater role to play in world relations. And the U.S. learned many lessons from the war itself. Therefore, although public opinion was relatively against the idea of establishing permanent or long-term military forces around the world, the nation had to evolve to set the foundation for its hegemonic role. Further, institutions including the CIA and the National Security Council (NSC) were established, and the Joint Chiefs of Staff was also subsequently created.
The changes made by the U.S. in the late 1940s made it more compatible with the greater role it sought in world order. These changes were by and large sufficient for the next half century until the U.S.S.R. collapsed in the late 1980s. The terror attacks of 9/11 then brought on the next evolution for the U.S., with the adoption of the Department of Homeland Security in 2002. The nation underwent additional adjustments to make the nation better geared and more efficient against acts of terror by creating the Director of National Intelligence, which narrowed the CIA and Department of Defense's scope. Indeed, at least partly because of the changes made by the U.S. in the 1940s and early 2000s, the country has been more safe in general and thus less vulnerable to threats and attempted attacks from the rest of the evolving world.
In this perspective, our organizations are an indispensable asset for the sake of our national security. However, if there came to be a point of prolonged peace, there would become a declining sense of necessity for these institutions. Even before that, though, prolonged peace could antiquate these institutions if for no other reason than a lack of work or target. This in turn could engender future vulnerability for the nation. To prevent this from happening, these institutions do what they can to remain relevant and needed by the nation, to provide the greatest possible sense of security for the government and the population. Perhaps it is ironic, or convenient, that in order to remain relevant and desired by the nation, these institutions pursue agendas that preserve the very threats that made them relevant in the first place, which works in contrast to the idea of eliminating threats and making the nation (and the world) safer overall.
For example, the Iran-Contra affair in 1985 was devised by the CIA, with the intent to secretly sell arms to an embargoed-Iran in exchange for the release of American hostages. This is perhaps within the realm of justification. But then, the deals proceeded to allow the U.S. to use the revenue from the arms sales to fund the Contras in Nicaragua against the communist regime there. Upon having the affair exposed to the world and to the American public, the CIA officials that were found responsible were pardoned by the administration. This deal, although aiding the effort to curb communism in Nicaragua, essentially did not make the world or the U.S. any more safe. Instead, it sowed the seeds for future conflict with Iran, which "conveniently" preserved the CIA's relevance in any such future altercation between the U.S. and Iran. And for those who may argue that the CIA's role ought to be justified for the (preferred?) sake of expanded democracy in South America (and inhibition of communism), I would respond with the Iranian coup d'état in 1953. In this case, the CIA was responsible for overthrowing the Iranian Prime Minister who sought to make Iran a full-fledged democracy. The catch was that upon proceeding with his plans to further democratize his country (which was supported by the Iranian public), Iran's oil industry was to be nationalized, which frustrated Great Britain. Therefore by overthrowing the Prime Minister and installing a puppet leader in his place, the U.S. and Great Britain would have better access to Iran's oil supply. All at the cost of a lost democracy. Whether by happenstance or not, to whatever extent that one considers Iran a "democracy" today, we are left with a combative Iranian mode of governance with the Ayatollah that has plagued the U.S. over time. But this is quite ideal for the CIA, who is all-too happy to continue to protect and "assist" us with the nuisance.
Of course, the CIA is only one of many institutions to have participated in events whose aim may or may not have served some good purpose nominally while accounting for its future relevance. Not always are such events even unlawful or scandalous, as the aforementioned CIA events were; many times they are just necessary as a cost of doing business. To provide an example related to current U.S. developments, in providing arms and training to the Afghan military, the U.S. Army seeks to strengthen Afghanistan internally as an ultimate ally of the U.S. But if the government in Afghanistan were to collapse (which arguably has a higher likelihood of happening if the U.S. and Afghanistan cannot reach a deal in the next six or so weeks), it could pose a problem for the U.S. Anti-Western sentiment among the Afghans, whether or not fueled by extremist groups, may then create a condition where the U.S. Army will again be needed to regain stability in the region and thus continue to serve long-run U.S. interests.
Thus, whether by genuinely innocent convenience or by design, our government's institutions play two roles: to serve and protect the national interests and overall security of our country, and to keep themselves alive and relevant. These roles can inherently work against each other as a conflict of interest. The last time that a government organization was disbanded happened in 1947, when the Department of Navy and Department of War combined to become the Department of Defense (then-named the "National Military Establishment"). The fact that there have not been any abolished government institutions in more than 60 years is by deliberate design; these institutions do what must be done to safeguard their existence. This is certainly not to say that we would be better off without them altogether - but to recognize and acknowledge that our national security can come at a mischievous, if not blatantly corrupt, price. While there have been many events over time that legitimately rationalized the need of these institutions by our nation, there is no doubt that the institutions will continue to engage in actions that perpetuate the very threats that brung 'em. And given the nature of national security itself, this phenomenon seems impossible to change.