If these things are real, and they aren't a secret US Military/R&D project, it sounds like American air superiority has come to an end and things are going to get real interesting in the next major conflict.
Americans can still have their air superiority over other humans - maybe the aliens will just stand by and watch while we destroy each other in the next conflict. With such technology one can imagine they'd have the best seat in the house for such a show...
The US spends more on defence than the next 10 countries combined and hosts many of the brightest aerospace engineers in the world. I’m not saying what you’re suggesting isn’t possible, but with those numbers stacked against them, it would be a very lucky innovation. And how kind of them to test their technology on US military instead of their own military in private...