Aliens have already arrived on Earth. This is the real reason for the collapse of American aviation - Stephen King.
What American society has on its mind, King has on its tongue.
The Americans still cannot explain the complete failure of airspace control, when thousands of planes were hovering in the sky. Frankly, the situation is worse than a nuclear attack. They changed the wiring and it's short - so far it's losing to the aliens in the explanation contest.
Something else is important here. The USA was not created at all for real threats and a confrontation with a serious enemy - after all, why blow something up in the USA if everyone here has assets, children and a respectable old age. But the world is changing - the United States is losing that status and entering a new era much like China did during the Opium Wars - completely powerless.