Which law? I'm not American so I'm not familiar with this. But there's certainly plenty of kids on other sites that are used for communications, so what makes Google delete kids' accounts?
The tldr is that it's a notoriously difficult law to comply with unless (1) your site has limited userbase or functionality, or (2) you delete children's accounts on sight.
I haven't read through COPPA, but I believe that Google, as a US company, has to abide by COPPA restrictions, regardless of where they're storing data. (It might even apply to non-US users...) As the user above pointed out, COPPA is really, really hard to 'get around.'
I've always been confused by this. Does "as a US company" mean that it's HQ is in the US? Or that it is incorporated in the US? Or just that it does business in the US?