They won't release clear videos for national security reasons, so they sure as heck aren't going to admit to something far more damning unless forced to do so.
I think "national security" is a bit overused and it needs to be considered in an all encompasing context. There are several reasons for that.
1. - to have advanced technology a country needs a very advanced industrial infrastructure, irrelevant from weather technology is secret or not. A good example is that no matter what they do China can't have 5 nm chips, because they are too advanced for them.
2. - if you don't have GDP that's big enough, you can't have what it takes even if you can partially make it. What I mean, Russia has 15 somewhat stealthy fighters, while NATO has a total of 1,500. Now, can 15 so-so healthy fighter planes stop 1,500 fighter planes? OK, one can throw in China, but China and Russia are not allies and they still don't tally up together to 1,500 stealth fighters.
But on the other side of the equation is
economic development of the nation. If UFOs were reverse engineered, for argument sake back in 60s, and made available to civilian sector, US GDP and living standard would be at least 100% higher than they are today. Not to mention that US and other developed nations would have commercially affordable way to stop global warming, begin mining asteroids, colonising Mars, begin beaming cheap solar energy from Earth's orbit, etc. etc. Economic benefits of reverse engineering anti-gravity tech are enormous and I completely agree with Dr. Greer in that.
That's why I say that hiding UFO information is an act of
national treason. It is equivalent to grievous bodily harm of one's own economy.