Keep Talking
The United States signed the United Nations Convention against Torture on 21 October 1994. Prior to this, from 1946-1948, we actually executed seven Japanese soldiers for committing torture during WWII, including the use of warterboarding.
Not just Japanese soldiers. American soldiers have been convicted for doing it.
How about the US soldiers court martialled during the Phillipine War for applying the 'water cure' ("Nothing can justify its use." - Theodore Roosevelt), or the American soldier court martialled for waterboarding a Vietnamese after that photo on the Jan. 21, '68 edition of the
Washington Post?
"Legality" is a red herring, as is the definition of "torture." Why even bring them up?
Laws and legal definitions have always been tailored to support whatever those in power want supported. They're changed with every shift of the political wind.