How is Livewire an actual threat to Superman?

She's a force of nature?

The answer will shock you.

I mean in the comics is Supes actually vulnerable to electricity enough for Livewire to be an actual threat to him like in the show?

Livewire isn't a threat to anyone in the comics. Even if comic-Supes wasn't far more powerful and durable than DCAU Supes, Simone decided that she'd take Livewire and job her into absolute oblivion in her premiere, then never let up on her until she became a worthless joke character.

So no, Livewire isn't a threat to anyone. At all.

The same can be asked for a majority of Supes rogue gallery.

Beata

Livewire should seriously consider the apprenticeship of Palpatine:

damn, Bruce Timm lied to me

Because one of Supes' less talked about weaknesses is electricity. Not that he's any weaker to it than anyone else, but he's not any stronger either. In the animated series, what seems to take him out more than even kryptonite is getting electrocuted.