If tomorrow it was announced that aliens were real, highly intelligent, and in communication with our governments, no one would be talking about it by Halloween
Seriously, I doubt it would even take that long. We get used to shit so quickly, and the news cycles have to keep feeding us new things, the only way we'd keep talking about the aliens if they kept doing new and interesting things. I'd be willing to bet a year later there would be some people who straight up forgot about it. "Oh yeah, aliens! Are they gonna, like, visit at some point or just keep exchanging calls with the Whitehouse?"
No, the US government didn't. There were some guys who allegedly heard some other guys talk about a crash that allegedly was a UFO. They all happened to work for the American government.
There were also a group of guys that wasted US government resources on just plain bullshit for literal decades.
Didn't one of the military branches release the Tictac video or something and admit they didn't know what the fuck it was? It's not an admission of aliens, but it kinda is an admission that UFOs exist.
Unidentified Flying Objects have always existed. In the US, around 99% of submitted cases were identified eventually or revealed to be bogus. The remaining 1% exist, but the track record of identified stuff doesn't give the alien explanation a high likelihood.