Because in my opinion we are already so superior that it will take the rest of the world 20 years to catch up, and that's if they even bother to try, which they probably will not.
Our recent fighter jet programs have all shown themselves to be huge wastes of money and resources that would've been better spent on systems and programs to prepare for the types of conflict we will be likely to face in the future.
There's a couple of interesting podcasts that deal with this subject if you'd like to dig into your question further and you want a recommendation. I can also point you toward some military think tank papers and articles as well.