I have to admit, I don't have even a decent understanding of what Manning leaked. My opinion would entirely depend on what was leaked and if it was "right" to leak it. And by "right" I mean my own personal, I know it when I see it, view of right and wrong. 35 years is a really long time to be locked up. Looking at wikipedia, it says Manning was acquitted of aiding the enemy, but found guilty of espionage and theft.
read the wikipedia article on her.
the most famous - or notorious - file leaked was video of a US Army Apache machine-gunning Iraqi civilians on the ground, and the cavalier attitude of the pilot (his audio transcript accompanied the video). There were also accounts of US massacres of Iraqi civilians, and thousands of diplomatic cables that contained embarassing information about US activities in Iraq and around the world... massacres, support for local dictators, etc.
Manning sent all this to wikileaks, which published it in 2010
Manning took steps to avoid disclosing any ongoing operational information that could put Americans in harms' way.
The tapes embarassed the US by: 1) showing that - holy fuck we did some pretty nasty things to the Iraqi people; and 2) exposing sloppy military & diplomatic security. granted, he was in an Army Intelligence unit, but still, why the hell did an Army private have access to all this confidential, classified information? Including diplomatic cables? Stupid.
Also, nothing Manning disclosed lead to any actual dangers to US troops or civilians, despite what government and media hacks like to claims. and that
came from testimony at Manning's court martial.
However... It did "harm US interests" depending on your point of view. it's been reported that the disclosures of massacres of Iraqi civilians by US troops lead to the Iraqi government refusing to grant immunity from Iraqi law to US personnel, so the US ultimately dropped the extension of force agreement and signed the withdrawal agreement (Bush negotiated it, Obama signed it).
"You won't let our troops massacre your people with impunity? we'll, I guess we'll be leaving then!"