Interrogated over what? He's publicly confessed repeatedly to what he's done. AQ subjects were tortured because the administration believed at the time they could find out about upcoming plots. Snowden has already done his business, boasted about it and fled the nation. If he ever set foot in the US he'd be very easily convicted by due process without needing to answer a single question.
I think a lot of people here just aren't aware of much of the history, or have forgotten.
An important reason for people being tortured was because of the Bush administration's torture policy described in John Yoo's "torture memos," which described a legal justification for the use of torture in early 2003 or so.
When this policy became a source of public humiliation around 2004-2005, the Bush administration began quietly and partially walking the policy back, and the CIA began destroying evidence.
It became an election issue around 2008, with Democrats successfully using the torture memos and Abu Ghraib to discredit Bush and the Republican party. The Republicans wisely chose McCain as their candidate, since he was a former POW who had been tortured and at least nominally opposed torture, but it wasn't enough to dispel the perceived taint of Abu Ghraib. This was one of the major reasons Obama was elected, and his public repudiation of the policy was one of the first major consequences of his election.
What happens if or when Snowden enters US custody depends on who is elected to which offices. The past 15 years should have taught us that the executive has a huge amount of leeway and that it can take years for the judicial branch to catch up, so that it actually matters more, rather than less, who is elected to what office. Elections determine the course of history. Make sure to vote, whether or not you are happy with the primaries.
Manning was convicted of espionage, imprisoned, and put into solitary confinement under the legal authority of UCMJ. Unfortunately, this is all legal, backed by the popular view that sentencing should be punitive and serve as a deterrent. Think of all the people in solitary confinement who, unlike Manning, were never in the public eye.
