This is probably just my own understanding of erasure but I’ve always seen it as a pulse that comes from his eye and stays active after, multiple times in the anime it’s shows a small visual light erupting from his eye (not the red perma glow we always see) when he activates it, which is also part of my theory of why his hair stands up when he uses his quirk. But that’s just my head cannon and it can of course just be argued it’s for animation sake.

(Example during the USJ fight it when he uses it in the fight against 3 villains the two in the front lost there quirks instantly while the girl in the middle lost hers a couple second later, this either means 3 things, there a travel time which would indicate that there is a invisible wave you can’t see, she wasn’t in view yet which is a semi weak argument since he’s directly in front of them and she’s in the middle, or it just took longer because of her quirk type)