I'm fairly certain the US legal system, when interpreting domestic cases (the purview of HIPAA) doesn't care about the GDPR. If a case crossed international boundaries, sure, but to say GDPR supersedes HIPAA is false. They apply to different jurisdictions, which are mostly, if not entirely, separate.
Agreed, the US is more lax. I was responding to the parent comment "I have submitted this because it is frequent to see on HN claims that IP addresses are personal data under GDPR"