On August 23, 2001, then director of the National Security Agency Michael V. Hayden dispatched the following missive to his underlings at the NSA.
Initially, I noticed the date of the DIR-GRAM, just 19 days and approximately three hours until the first plane smashed into the WTC. I briefly wondered what the results would have been had the poll been taken on 9-11 until I realized that internet polls are bullshit and that few of those voting in this poll had any knowledge of the American national security appartus on which to base their vote. I could not track down the original poll, most likely long since deleted or purged from the History Channel website, but I doubt they included lesser-known agencies like NCIS (I know NCIS is famous now, but the show that made it famous came out in 2003).
The fourth paragraph was the most striking. While Hayden conceded that "we [The NSA] cannot draw too much from the poll's conclusions, it is encouraging to see tangible evidence that more Americans understand that our purpose and mission has less to do with the film "Enemy of the State," and more to do with protecting the hard won freedoms and liberties that we all enjoy."
However, the NSA is probably the most opaque intelligence operation in the Western world and it only got more secretive after the 9-11 attacks. As I mentioned above, few voters in that poll possessed any relevant knowledge with which to form their judgment. I doubt any study has ever been conducted to determine which of the myriad of intelligence agencies operating in the United States has been the most effective in protecting the United States. What Hayden was or should have been gloating about is that History Channel poll, as much as any online poll can tell you can tell you anything useful, is that the NSA's public relations effort had, at that point, convinced Americans to trust the NSA in terms of both its effectiveness and its trustworthiness.