>How would be the US now without Luigi Mangione?

More or less the same except a family of kids would not be missing their father and grow up with the idea of wanting to get revenge on their father's murderer. An eye-for-an-eye never makes good societies which is why all civilized countries outlawed their practice.

>Would Palantir or Flock disappear?

The more elites you murders, the more of your tax dollars the elites will send to the military and law enforcement to better protect them from you and the more of your tax dollars they'll send to Palantir and Flock to spy on you. You can't win this by killing elites, they have more money, more guns than you and their guns are bigger and more powerful than yours. You win by enacting change through popular votes.