I have made it clear that IF the NSA is part of the unconstitutional Administrative State, then it is unconstitutional. Pretty clear.
You seem to not understand that the fourth branch of the federal government, the Administrative State, is unconstitutional. The Constitution does not authorize this unaccountable branch that apparently no one really knows how big it really is nor who these rogue agencies report to. Federal tyranny run amok.
Congress creating something or not creating something is NOT the standard of constitutionality. THE CONSTITUTION ITSELF as written and originally understood and intended is the standard. So Truman creating something with congressional authorization does not per se mean it is constitutional.
If the NGA is part of the Administrative State, then it is unconstitutional.
If you are barking about an action Truman did, and no one made any objection...then it's probably a battle you are not going to win, even if you are right. It seems the Director of the CIA had a good idea, sent it to the Deputy NSC, and then it went to Truman. I'd have to dig into the archives to see what deal was made for funding, but it could not have been implemented without some acknowledgment from Congress that it need to be secret, and it needed to be built.