Acmetropolis is Acme Acres, and by extension, Earth.Some time in the future, the Acme Corporation became a government-controlling Mega Corp., and expanded Acme Acres until by 2772 it became a planet-wide city.
This series is a Stealth Parody of both Looney Tunes and action series in general that was never meant to be taken seriously.Everything about the show itself supports this.
Descendants of the characters from Tiny Toons, Animaniacs, Histeria!, Freakazoid!, and Road Rovers also live in this world.Since it was established that the characters from all these shows lived in the same world as the Looney Tunes characters, no doubt their descendants also exist in the same time period as the Loonatics.
Duck Dodgers takes place within the same universe.This troper has noticed alot of Mythology Gags with both shows. Such as the setting in space, the crime fighting organisations and the Planet Blanc. It's possible that Loonatics Unleased takes place many years afterwards.
The powers the heroes gained were simply inactive before the meteor.Because Slam, Tech, and Rev have the same powers as their ancestors. Danger Duck too, since Daffy had been shown to disappear behind an object and reappear elsewhere. Somewhere along the line they lost those capabilities, but got them back through the meteor strike.