> This kind of tech could only come from a superpower, and you really think they wouldn't brag about it? They would not. How long were stealth bombers a closel

> This kind of tech could only come from a superpower, and you really think they wouldn't brag about it? They would not. How long were stealth bombers a closely held secret? If these are craft, then they are far beyond even that. Once you know something is possible, you're halfway to solving it. If other nations knew the US had some fantastical tech, they would up their espionage and research efforts around the specific characteristics they've seen and quickly reproduce it.