"Global problems require global solutions." It sounds crazy, but a staged alien invasion could very well be the catalyst for bringing in some form of global governance. We've already seen what TPTB have been able to achieve using the Covid panic. Any threat, real or fabricated, that affects everyone worldwide can be used to demolish massive amounts of civil liberties for "the greater good".

It's not really so hard to believe it's possible. Militaries everywhere no doubt have all sorts of advanced aerospace technology that is kept top secret. Since ordinary citizens don't have access to the advanced sensors and satellites that would be used to detect the "aliens", officials can claim whatever they want and no will be able to verify it. I recommend this video for a deeper explanation of what could be.

However, I don't believe this is coming any time soon. This is a situation that would probably be the final keystone to finalize their system of total control only after all the groundwork has been laid, such as EU-like unions around the world. People would not be so willing to accept total centralization of power unless the world was already mostly centralized.