Why should a US company harm UK citizens just because they're in the US?
If you want to serve a market in another country you have to follow their rules.
In this case, Imgur have been misusing UK children's information. Considering the laws are pretty similar, I suspect they're misusing EU children's information too.
That's the OP's question. Bluntly: if I'm here, and they're bloviating over there, what can they actually do about it?