if character A steps out of the film/animatic their fighting Character B in and destroys said 2 dimensional platform, I would qualify that more as Reality Sundering or just straight up existence erasure that the opposing foe would need some Acausality to even survive. Should theoretically be universe level, though Looney Tunes is an anthology of events stretched out episodically with the tunes having different lives/jobs/names and living in entirely different locations so you could probably argue some pocket dimension stuff. If we count Space Jam as "canon" the Looney Tunes verse is literally just a space that exists in the center of the Earth.