While Young Justice is able to defeat all the attempts at takeover, destroy The Light and stop the destruction of the planet by Mongul and his War World weapon, the populace would clearly remain shaken by such events.
For those who have forgotten, seeing as how it’s been almost six years since Young Justice was on the air, the first season of the series saw several Justice League members, who had been magically enslaved by the secret supervillain group known as The Light, travel off world and attack a peaceful planet.
During Season 2, which took place five years after the events of Season 1, the consequences of that attack are brought back to Earth, as several alien forces come here in an attempt to try to takeover now that they know about our metahumans and see us as viable potential members of their empires.