As has been made clear by the Senate and House hearings the last two years, the “they” who have withheld the information boils down to the Executive Branch (the Presidents), and their military and security agencies.
Ask yourself a question (or envision a “thought experiment”).
You’ve just been elected President of the US, the “most powerful person in the world.” You have a press conference and announce that there is a non-human intelligence that we have been interacting with for some 80 years, and that we are attempting to replicate their much more advanced technology.
What will be the first question to you?
“Can we stop them if they become aggressive?”
Mmmmmmm.
How do you answer that question?
Will it be easy for “the most powerful person in the world” to openly admit potential impotence against non-human technology?