How has that hurt the USA?
You may not be aware of this, but it is technically public knowledge: the information security parameters that allowed Manning access to classified data of such a wide range are the result of 9/11, whereafter it was determined that federal authorities may have had a better chance of preventing the tragedy if the various intelligence and intelligence-related agencies collaborated and pooled their data. Prior to that time, the intelligence community was stovepipe-organized, with each agency keeping their information to themselves and guarding what they saw as their "territory". In response, agencies were encouraged to pool intelligence so that law enforcement and military analysts could access it all and develop a "bigger picture" that would help them do their jobs better.
Recently some agencies have withdrawn their participation in the "pool" explicitly in response to the Wikileaks affair - most notably the State Department - because obviously the DoD has rodent issues. This is a tremendous step backward for American anti-terrorism efforts, and intelligence analysis in general, and might easily contribute to the success of an attack they may otherwise have been prevented with the help of intel that's no longer being shared by the spooked agencies.
In addition, contrary to popular opinion (which seems to be that "classification is spiraling out of control"), the trend lately is ever-slightly-more transparency; what with the passage of the FOIA act, overhauls of classification systems, and whatnot. Did you know, for example, that last year for the first time in US history, America's intelligence budget was publicly released on the numbers? Before, it had been "hidden" by simply being included in general funds or specific agencies' and departments' overall budgets, and secretly earmarked "after taxes", as it were. Tiny steps, to be sure, but in the right direction. The Wikileaks affair has thrown a stick in that bicycle's spokes, and agencies are being ordered to clamp down on secrecy and information security like never before. Manning actually short-circuited the slow but real progress of the federal government away from Cold War-era classification policy.
Hope this helps.