I understand. But out of curiosity: why is there no material evidence across the different civilizations. Surely all of humanity couldn't be duping themselves and only US is speaking up in 21st century.

I am _not_ a non-believer. It is just the lack of scientific historicity and diversity of evidence that bothers me. I cannot reconcile that mountain of contradiction with the current testimony. It is one Congressional account of definitive existence, versus the absence of conclusive proof or material evidence anywhere else.