Firstly, the US government has greater authority and ability to fine or otherwise leverage financial action against companies incorporated in the US.
Secondly, Facebook leadership has been repeatedly called to testify in front of Congress for various reasons in recent years, and in doing so has been held accountable for numerous failures. In August of last year they paid out $725 mil in a class action lawsuit. Although not US, still NATO example: In May of 2023 they were fined 1.2b euros for breach of data by the UK.
They were also recently called to testify in front of US congress about the online child exploitation crisis.
Granted they make billions, but they are getting punished for mismanagement, both publicly and financially. It may be a drop in the bucket, so to speak, but it’s been enough for them to change their policies and practices over the years.