I don't think the US Government had anything to do with it (at least not promoting it). People LOVE conspiracy theories. Take some people to a regular little league game and they'll start looking for the "real truth" and before long they think Elvis is alive and coaching the other team.
In reality, I'd wager that UFO's as reported, are LARGELY simply made up claims, hoaxes, or simply regular aircraft (in which case it WAS unidentified to the original observer, just not anyone with any sense

). The remainder of the cases are quite possibly test aircraft by the government, but while they always have some "top secret" projects - it's not as far fetched as people would imagine. Technology advances in very small increments. Anything they're testing likely isn't all that more advanced than what we have now.
What happened is a lot of people just take that stuff and run with it because to them it's exciting. No government involvement needed.
Personally, given the sheer, unimaginably immense size of the universe I most wholeheartedly believe that there is other life other there - I just don't think we're seeing it in our skies

. Put it this way - there are at least 3,000,000,000,000,000,000,000 stars in the universe - 100 billion galaxies an average of 30 billion stars per galaxy - some have more, some less, but that's a good ballpark - around half likely have a planetary system. Now, the odds of a planetary system containing a planet that can support life is likely pretty rare. I'd wager extremely rare. When you roll the dice not just billions of times though, but billions of billions of times, then you're bound to hit jackpot a lot even with bad odds

. However, with that immense size, also comes immense DISTANCE. The laws of physics come into play. Physically visiting other civilizations will be unlikely - ever. I don't see them visiting us, nor us visiting them. The best we could likely hope for would be radio contact, but even that is unlikely in my opinion.